Encapsulant sheet for self-luminous display or encapsulant sheet for direct backlight, self-luminous display, and direct backlight

ABSTRACT

An encapsulant sheet suitable for encapsulating a light-emitting element in, for example, a self-luminous display or for direct backlights. The encapsulant sheet is a single-layer or multi-layer resin sheet that includes an adhesive layer exposed at a topmost surface. The Vicat softening point is greater than 60° C. and no higher than 100° C. The melt viscosity of the encapsulant sheet, at a shear velocity of 2.43×10 sec −1  and measured at a temperature of 120° C. is at least 5.0×10 4  poise and no more than 1.0×10 5  poise. The adhesive layer contains a polyolefin and a silane component, and a content of the silane component relative to the resin component of the adhesive layer is at least 0.03% by mass and less than 10% by mass.

This is a Continuation of application Ser. No. 18/078,457 filed Dec. 9,2022, which is a Continuation of application Ser. No. 17/058,443 filedNov. 24, 2020, which issued as U.S. Pat. No. 11,550,186, which is aNational Phase of International Application No. PCT/JP2019/020779 filedMay 24, 2019, which in turn claims the benefit of JP 2018-099952 filedMay 24, 2018, JP 2018-140518 filed Jul. 26, 2018, and JP 2018-110790filed Jun. 11, 2018. The disclosure of each of the prior applications ishereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates an encapsulant sheet for self-luminousdisplays or for direct backlights, a self-luminous display, and a directbacklight.

BACKGROUND ART

The development of a self-luminous display for which a micro-LEDtelevision is representative has been advancing as a next generationdisplay device in place of various display devices of liquid crystaltype (Patent Document 1).

-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. 2018-14481-   Patent Document 2: Japanese Unexamined Patent Application,    Publication No. 2017-9725-   Patent Document 3: Japanese Unexamined Patent Application,    Publication No. 2014-148584

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present disclosure has an object of providing a suitable encapsulantsheet for encapsulating of light emitting elements in a self-luminousdisplay or the like.

Means for Solving the Problems

One of the embodiments of the present disclosure is an encapsulant sheetfor self-luminous displays or direct backlights, which is a resin sheetwith polyolefin as the base resin, in which the melt viscosity measuredat a temperature of 120° C. and at a shear rate of 2.43×10 sec⁻¹ is atleast 5.0×10³ poise and no more than 1.0×10⁵ poise.

Another one of the embodiments of the present disclosure is anencapsulant sheet for self-luminous displays or direct backlights, whichis a single-layer or a multi-layer resin sheet configured to include anadhesive layer exposed at the topmost surface, in which the adhesivelayer contains polyolefin and a silane component, and content of thesilane component relative to the resin component of the adhesive layeris at least 0.02% by mass and no more than 0.15% by mass.

Another one of the embodiments of the present disclosure is anencapsulant sheet for self-luminous displays or direct backlights, inwhich one surface is an adhesive surface, and the other surface is apeeling surface, the adhesive strength of the adhesive surface measuredby a predetermined adhesion test explained below is at least 5.0 N/15 mmand no more than 50.0 N/15 mm, and the adhesive strength of the peelingsurface is at least 0.1 N/15 mm and no more than 3.0 N/15 mm.

Effects of the Invention

According to the present disclosure, a suitable encapsulant sheet forencapsulating light emitting elements of self-luminous displays, etc., aself-luminous display made using this, and the like are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view and a partially enlarged plan view of an imagedisplay surface of a self-luminous display made using LED modules forself-luminous displays in which an encapsulant sheet of a firstembodiment is laminated on a light emitting module;

FIG. 2 is a sectional view representing a cross section of the A-Aportion in FIG. 1 ;

FIG. 3 is a perspective view of an LED element constituting an LEDmodule for the self-luminous displays in FIG. 1 ;

FIG. 4 is a sectional view which schematically shows an example of alayer configuration of an encapsulant sheet of a third embodiment;

FIG. 5 is a diagram presenting an explanation of a production method ofLED modules for a self-luminous display made using the encapsulant sheetof the third embodiment;

FIG. 6 is a diagram which is a partially enlarged view of FIG. 5 ,presenting an explanation of an aspect of placement of the encapsulantsheet, relative to a heated plate of a laminator;

FIG. 7 is a perspective view which schematically shows an example of aconfiguration of an LED display device made using a direct LED backlightof a fourth embodiment; and

FIG. 8 is a partially enlarged cross-sectional view of the periphery ofan installation area of one LED element, in an LED display device madeusing the direct LED backlight of the fourth embodiment.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments (hereinafter called “present embodiment) of thepresent disclosure will be explained. It should be noted that“polyolefin” in the present embodiment is synonymous with “olefin-basedresin” and “olefinic resin”.

First Embodiment Encompassed by Present Embodiment

More specifically, the first embodiment provides the followingconfiguration.

A first aspect of the present invention is an encapsulant sheet forself-luminous displays or direct backlights, in which the encapsulantsheet is a resin sheet with polyolefin as a base resin, in which meltviscosity of the encapsulant sheet measured at a shear rate of 2.43×10sec⁻¹ at a temperature of 120° C. is at least 5.0×10³ poise and no morethan 1.0×10⁵ poise.

The first aspect of the present invention emphasizes the viscosity ofthe base resin during hot pressing in the encapsulant sheetencapsulating an electronic device, and optimizes the melt viscosity ata temperature of 120° C. to within a predetermined range. It is therebypossible to achieve at high levels both the molding property during hotpressing of the encapsulant sheet, and suppression of squeezing out ofresin caused by excessive flow. Then, it is further possible tofavorably maintain uniformity in the film thickness of the encapsulantsheet after hot pressing. In this way, according to the first aspect ofthe present invention, it is possible to obtain an encapsulant sheetsuperior in suitability for a self-luminous display such as a micro LEDtelevision.

According to a second aspect of the present invention, in theencapsulant sheet as described in the first aspect, melt viscosity ofthe encapsulant sheet measured at a shear rate of 2.43×10 sec⁻¹ andmeasured at a temperature of 120° C. is at least 5.0×10⁴ poise and nomore than 1.0×10⁵ poise.

According to the second aspect of the present invention, it is possibleto maintain the uniformity in film thickness after hot pressing whichinfluences the display quality of images, etc. on the self-luminousdisplay such as a micro LED television, at a higher level than the firstaspect of the present invention.

According to a third aspect of the present invention, in the encapsulantsheet as described in the first or second aspect, Vicat softening pointis greater than 60° C. and no higher than 100° C.

The third aspect of the present invention sets the Vicat softening pointfor the encapsulant sheet described in the first or second aspect to ahigh temperature range differing from a conventional article such as asolar cell module. It is thereby possible to more reliably suppress theoccurrence of blocking in the manufacturing process of self-luminousdisplays made using the encapsulant sheet, and contribute to animprovement in productivity of self-luminous displays. On the otherhand, by setting this temperature range to no higher than 100° C., it ispossible to sufficiently maintain the molding property on the orderdemanded in encapsulant sheet for self-luminous displays.

According to a fourth aspect of the present invention, in theencapsulant sheet as described in any one of the first to third aspects,the encapsulant sheet is a resin sheet which is black, white or anothercolor.

The fourth aspect of the present invention establishes the encapsulantsheet for self-luminous displays as described in any one of the first tothird aspects as a colored encapsulant sheet. For example, byestablishing these encapsulant sheets for self-luminous displays as acolored resin sheet to which a desired color is imparted optically, itis possible to arrange the encapsulant sheet as an optically functionallayer that combines an optical characteristic required in theself-luminous display together with the original protective function oflight emitting elements of the encapsulant sheet. More specifically, forexample, by establishing the encapsulant sheet as described in any oneof the first to third aspects as a black resin sheet, for example, sinceit is possible to form a layer combining the functions of an encapsulantmaterial and a light-shielding layer, it is possible to significantlyimprove the productivity of self-luminous displays, while achieving theabove respective effects possessed by the encapsulant sheet as describedin any of the first to third aspects.

According to a fifth aspect of the present invention, in the encapsulantsheet as described in any one of the first to fourth aspects, theencapsulant sheet is a single-layer or a multi-layer resin sheet and theencapsulant sheet includes an adhesive layer exposed at a topmostsurface,

-   -   wherein the adhesive layer contains a resin component and a        silane component,    -   wherein the resin component includes a polyolefin, and    -   wherein content of the silane component relative to resin        component of the adhesive layer is at least 0.02% by mass and no        more than 0.15% by mass.

The fifth aspect of the present invention establishes the base resin asa thermoplastic polyolefin in the encapsulant sheet of the first tofourth aspects, and moreover, contains a silane component in a contentof a specific range, in a state in which a majority of silane componentis graft-polymerized to this polyolefin. It is thereby possible toobtain an encapsulant sheet combining a balance of adhesion durabilityto a circuit board during use of the self-luminous display which is thefinal product, and reworkability in a manufacturing stage process. Itshould be noted that the details of the invention according to the fifthto seventh aspects are explained in the second embodiment.

According to a sixth aspect of the present invention, in theencapsulation sheet as described in the fifth aspect, the silanecomponent includes a graft silane component which graft-polymerizes tothe polyolefin of the adhesive layer, wherein the adhesive layercontains at least 70% by mass and no more than 100% by mass of the graftsilane component with respect to the silane component.

According to the sixth aspect of the present invention, it is possibleto more reliably acquire the above-mentioned effects which can beexerted by the fifth aspect of the present invention, in a product lifecycle from manufacture to use of a general micro LED television. Inparticular, it is possible to significantly improve the stability of theproduct quality of the encapsulant sheet from manufacturing completionof the encapsulant sheet until incorporated into the final product.

According to a seventh aspect of the present invention, in theencapsulant sheet as described in the fifth or sixth aspect, theencapsulant sheet is a multi-layer resin sheet in which the adhesivelayer is laminated on a base layer with polyethylene as a base resin.

According to the seventh aspect of the present invention, theencapsulant sheet as described in the fifth or sixth aspect isestablished as a resin sheet of multi-layer configuration furtherincluding a base layer in addition to the adhesive layer. By configuringthe base layer by a resin more superior in heat resistance, it ispossible to establish as an encapsulant sheet superior in other physicalproperties such as heat resistance, while securing each effect which canbe exerted by the fifth or sixth aspect of the present invention in theadhesive layer.

According to an eighth aspect of the present invention, in theencapsulant sheet as described in any one of the first to seventhaspects, one surface is an adhesive surface, and the other surface is apeeling surface, adhesive strength of the adhesive surface measured byan adhesion test is at least 5.0 N/15 mm and no more than 50.0 N/15 mm,and adhesive strength of the adhesive surface measured by an adhesiontest is at least 0.1 N/15 mm and no more than 3.0 N/15 mm. The adhesiontest measures adhesive strength of each surface by adhering a surface ona side serving as a measurement target of an encapsulant sheet samplecut to a width of 15 mm onto a blue-sheet glass plate (75 mm×50 mm×3 mm)and performing lamination processing in a vacuum heated laminator at140° C. for 10 minutes, and performing a vertical peeling (50 mm/min)test with a peel tester on the encapsulant sheet sample adhered on theblue-sheet glass plate.

In the eighth aspect of the present invention, the encapsulant forself-luminous displays is established as a resin film having anasymmetrical layer configuration of different adhesive strengths, at onesurface (adhesive surface) and another surface (peeling surface). It isthereby possible to obtain an encapsulant sheet combining adhesivenessto a circuit board surface having fine unevenness, and moldreleasability from a heated plate on which placed during thermallamination processing, and possible to produce LED modules forself-luminous displays with higher productivity, while keeping qualitywhich is at least equal to conventional, even without using a moldrelease film. It should be noted that the details of the inventionaccording to the eighth to tenth aspects are explained in the thirdembodiment.

According to a ninth aspect of the present invention, in the encapsulantsheet as described in the eighth aspect, the encapsulant sheet is amulti-layer resin sheet having an adhesive layer exposed at a surface ona side of the adhesive surface, and a non-adhesive layer exposed at asurface on a side of the peeling surface, the adhesive layer contains asilane component in a proportion of at least 0.02% by mass and no morethan 0.19% by mass relative to resin component, and the non-adhesivelayer does not contain the silane component, or in a case of containingthe silane component, content relative to resin component is less than0.02% by mass.

According to the ninth aspect of the present invention, a suitableamount of silane component is contained in the adhesive layer formingthe adhesive surface, and silane component is either not contained inthe non-adhesive layer forming the peeling surface, or even ifcontained, is limited to less than a very small amount. It is therebypossible to control the adhesive strength of each layer to a favorablerange, and more reliably acquire the above effects which can be exertedby the eighth aspect of the present invention.

According to a tenth aspect of the present invention, in the encapsulantsheet as described in the eighth or ninth aspect, the encapsulant sheetis a multi-layer resin sheet in which the adhesive layer is laminated onone surface of the base layer with polyethylene as base resin, and thenon-adhesive layer is laminated on the other surface of the base layer.

According to the tenth aspect of the present invention, the encapsulantsheet as described in the eighth or ninth aspect is established as aresin sheet of three-layer configuration made by the adhesive layer andnon-adhesive layer respectively being laminated to both surfaces of thebase layer. According to this, it is possible to easily produce anencapsulant sheet for which the adhesive strength of each layer iscontrolled appropriately, by coextruding of resin compositions havingrespectively different contents of adhesive component, and possible tofurther establish as an encapsulant sheet superior in productivity,while securing the respective effects which can be exerted by the eighthor ninth aspect of the present invention.

An eleventh aspect of the present invention is a self-luminous displaycomprising: the encapsulant sheet as described in any one of the firstto tenth aspects; a display panel; and a light emitting module in whicha plurality of light emitting elements is mounted to a wiring substrate,in which the encapsulant sheet is laminated to the light emitting moduleto cover the light emitting elements and the wiring substrate, and thedisplay panel is laminated to the encapsulant sheet.

According to the eleventh aspect of the present invention, it ispossible to acquire the above respective effects which can be exhibitedby the encapsulant sheet of any of the first to tenth aspects, andobtain a self-luminous display superior in optical characteristics,durability and productivity.

According to a twelfth aspect of the present invention, in theself-luminous display as described in the eleventh aspect, the lightemitting element is an LED element.

The twelfth aspect of the present invention is an application of thefirst embodiment to various self-luminous type LED display devices ofwhich a micro LED television expected as mainstream of next generationmonitors is representative. It is thereby possible to obtain aself-luminous type LED display device superior in opticalcharacteristics, durability and productivity.

According to a thirteenth aspect of the present invention, in theself-luminous display as described in the twelfth aspect, the LEDelement has an LED light emitting chip and a resin cover which coversthe LED light emitting chip, width and depth of the LED element are bothno more than 300 μm, and height is no more than 200 μm, and anarrangement interval of each of the LED elements is at least 0.03 mm andno more than 100 mm.

The thirteenth aspect of the present invention is applying theself-luminous display of the twelfth aspect to a high-definitiondot-matrix display device or the like, made by densely mounting LEDelements in a chip-on-board format directly mounting many LED chips onthe board. It is thereby possible to obtain a high-definition LEDdisplay device superior in optical characteristics, durability andproductivity.

According to a fourteenth aspect of the present invention, in theself-luminous display as described in the thirteenth aspect, width anddepth of the LED element are both no more than 50 μm, and height is nomore than 10 μm, and an arrangement interval of each of the LED elementsis at least 0.05 mm and no more than 5 mm.

The fourteenth aspect of the present invention is applying theself-luminous display of the thirteenth aspect to a “micro LEDtelevision” for which development has advanced in recent years and isexpected as a next generation video display device. It is therebypossible to obtain an ultrahigh-definition LED display device superiorin optical characteristics, durability and productivity.

According to a fifteenth aspect of the present invention, theself-luminous display as described in any one of the eleventh tofourteenth aspects includes a light emitting surface made by a pluralityof the light emitting module being joined on the same plane, wherein theencapsulant sheet is laminated on the light emitting surface.

The fifteenth aspect of the present invention carries out enlargement ofthe screen size of various self-luminous displays including a micro LEDtelevision, by joining a plurality of LED modules for self-luminousdisplays configured using the encapsulant sheet as described in any oneof the eleventh to fourteenth aspects. The encapsulant sheet asdescribed in any one of the eleventh to fourteenth aspects is superiorin surface smoothness after joining by thermal lamination; therefore, itis possible to perform screen enlargement of the self-luminous displaywith a high degree of design freedom, without causing a decline inscreen quality accompanying the joining of the above-mentioned modules.

According to the first embodiment, it is possible to provide anencapsulant sheet which is preferable in various self-luminous displayapplications such as micro LED televisions.

In the self-luminous display, an encapsulant sheet for protecting lightemitting elements is laminated on the surface on the light-emittingsurface side of an LED module configured by light emitting elements suchas LED elements being mounted on a wiring substrate (Patent Document 2).

For the encapsulant sheet for electronic devices disclosed in PatentDocument 2, application to various electronic devices including solarcells, etc. has been widely anticipated, and the Vicat softening pointthereof is demanded to be in a low temperature range of no higher than60° C., and more preferably no higher than 30 to 50° C. This is plannedas “exhibiting high adhesiveness due to thermocompression in a shorttime” as disclosed in this document. Furthermore, in the past, even uponensuring sufficient filling-in property (molding property) of theencapsulant sheet into the unevenness of the surface of electronicdevices of various surface forms, it has been considered preferable forthe Vicat softening point to be within the above-mentioned lowtemperature range.

However, in self-luminous displays, a special “uniformity in the filmthickness” is required in the encapsulant sheet laminated on thelight-emitting surface side of the LED elements. If the film thicknessin the central part and the film thickness of the end part of thisencapsulant sheet slightly differs, the encapsulant sheet becomes alenticular state, and will have an untended adverse optical effect onthe display quality of the micro LED display device.

In the course of the development of the aforementioned micro LEDtelevision, in the case of the surface of an electronic device which isthe target of coating by the encapsulant sheet only having minuteunevenness as in the light emitting surface of the above-mentioned LEDmodule constituting the micro LED television, for example, and moreover,the uniformity in film thickness of the encapsulant sheet after hotpressing being demanded at a much higher level than the case of a solarcell module or the like in order to maintain video quality, there hascome to be doubt in whether the encapsulant sheet having a Vicatsoftening point in the above such low temperature range can necessarilybe considered optimal.

In the production of a self-luminous display, it is not necessary tolimit the Vicat softening point to the above such low temperature range(no higher than 60° C.), as in the encapsulant sheet for conventional,common electronic devices. Then, the occurrences of defects unique tothe aforementioned self-luminous displays are caused by excessive flowof the resin forming the encapsulant sheet during hot pressing.Consequently, in order to more reliably avoid the occurrence of thesedefects, after ensuring the required molding property, it is importantto reliably suppress excessive flow of the resin forming the encapsulantsheet.

In the case of selecting a resin by focusing on the fluidity during hotpressing, conventionally, the value of MFR is widely adopted as an indexthereof. However, although the value of MFR becomes a measurement at190° C. in the case of measuring based on JIS K6922, this temperaturediverges from the temperature upon the encapsulant sheet forself-luminous display actually melting during hot pressing; therefore,the present inventors have come to find a problem in that, even ifoptimizing the value of MFR, it is not possible to necessarily optimizethe behavior of the resin upon hot pressing.

In such a situation, development of an encapsulant sheet specialized asa preferable sheet for various self-luminous display applications suchas micro LED televisions for which the expectation as a next generationdisplay device is rising has been desired.

The first embodiment has been made taking account of the above suchsituation, and has an object of providing an encapsulant sheet superiorin fitness for self-luminous displays such as a micro LED television.

The present inventors thoroughly researched, a result of which foundthat it is possible to use as a sheet preferable in self-luminousdisplay applications, by focusing on the melt viscosity particularly ata temperature of 120° C., and maintaining this at the specific meltviscosity, thereby arriving at completing the first embodiment.Hereinafter, the first embodiment will be explained more specifically.

(Self-Luminous Display)

“Self-luminous display” is a display device for which the micro LEDtelevision exemplified above is representative, and is a display deviceof visual information such as text, images and video. This displaydevice is a display device which can display the above-mentioned visualinformation directly onto a display screen by mounting a large number ofmicro light emitting elements in a matrix pattern on a wiring substrate,and flashing each light emitting element by selectively illuminatingeach light emitting element by way of light emission control meansconnected thereto.

The encapsulant sheet for self-luminous displays (hereinafter simplyreferred to as “encapsulant sheet”) can be preferably used in LEDdisplay devices using LED elements as the light emitting elements, among“self-luminous displays”. In addition, the LED elements in this case aremore preferably “micro-sized LED elements”. In the first embodiment,“micro-sized LED elements” specifically shall refer to an LED elementfor the size of the overall light emitting element including the LEDlight emitting chip and a resin cover which coats this, in which thewidth (W) and depth (D) are both no more than 300 μm, and height (H) isno more than 200 μm (refer to FIG. 3 ).

Regarding the size of this “micro-sized LED elements”, it is morepreferable for the width and depth to both be no more than 50 μm, andthe height to be no more than 10 μm. It should be noted that this sizerange is a standard size range of LED elements mounted to a micro LEDtelevision for which development has advanced in recent years, and hasbeen anticipated as becoming the main stream of next generationtelevisions. Hereinafter, in the first embodiment, the self-luminousdisplay in which micro-sized LED elements having width and depth both ofno more than 50 μm, and height of no more than 10 μm are arranged in amatrix form at a pitch of several μm to several tens of μm, in a numberon the order of at least 1000×1000 is called a “micro LED displaydevice”.

Then, a detailed explanation will be made, while adopting an embodimentof a case of the “self-luminous display” below being a “micro LEDdisplay device” as a specific preferred example among the variousembodiments. However, the technical scope of the present embodiment isnot limited to only the application to the “micro LED display device”.It is technology which is applicable to all “self-luminous displays”according to the aforementioned definition.

(Micro LED Display Device)

FIG. 1 is a front view of a micro LED display device 100 which is anembodiment of the self-luminous display, and a partial enlarged viewthereof (100A). In addition, FIG. 2 is a cross-sectional viewrepresenting a cross section of the A-A portion in FIG. 1 , and is adiagram providing an explanation of the layer configuration of the microLED display device 100 shown in FIG. 1 . This micro LED display device100 is a self-luminous display device including an “LED module 30” thatis a “light emitting module” for a self-luminous display in which alarge number of micro-sized “LED elements 10” as “light emittingelements” are mounted to a wiring substrate 20. For each LED element 10,the light emission thereof is controlled independently by a lightemission control means (not illustrated) such as an IC chip boardseparately joined.

In the present embodiment, although the module in which light emittingelements are mounted to a wiring substrate is generally termed as alight emitting module, in the micro LED display device 100, an LEDmodule 30 in which a large number of LED elements 10 are mounted to thewiring substrate 20 corresponds to this light emitting module.

Then, in the micro LED display device 100, the encapsulant sheet 1 forself-luminous display of a second embodiment is laminated in a statecoating the LED elements 10 and wiring substrate 20 on the surface onthe side of the LED module 30 on which the LED elements 10 are mounted.Then, a display panel 2 such as various optical films and transparentprotective glass is further laminated onto an outer surface side of theencapsulant sheet 1 (display surface side of micro LED display device100).

A plurality of LED modules 30 for self-luminous displays is joined inmatrix form on the same plane, and the encapsulant sheet 1 is laminatedsimilarly to as described above on the joined LED modules, whereby it ispossible to configure LED modules for large-scale self-luminousdisplays, and further, large-scale micro LED display devices.

(Production Method of Micro LED Display Device)

The micro LED display device 100 can be produced by making a laminatebody which layers the LED module 30 for self-luminous displays in whichthe LED elements 10 are mounted to the wiring substrate 20, encapsulantsheet 1, display panel 2, and other optical member arranged asnecessary, and integrated this laminate body by hot pressing. It shouldbe noted that the part of the laminate member is preferably connected inadvance by adhesive before the above-mentioned hot pressing asnecessary. The encapsulate sheet 1 of the first embodiment exhibitssufficient molding property during hot pressing for integration as thisfinal product, and is superior in uniformity of film thickness afterthis hot pressing.

(LED Module)

The LED module 30 which is a light emitting module for self-luminousdisplays, as shown in FIG. 2 , is configured by the LED elements 10being mounted to a wiring substrate 20 in which wiring 22 is formed in asupport substrate 21.

The wiring substrate 20, as shown in FIG. 2 , is a circuit board made bythe wiring part 22 formed from a metal such as copper and otherconductive members being formed, in a form capable of conducting withthe LED elements 10, on the surface of the support substrate 21. Thesupport substrate 21 may be a hard substrate such as a conventionallyknown glass epoxy substrate or glass substrate as the substrate of anelectronic circuit, or can be established as a substrate made of resinhaving flexibility such as polyethylene terephthalate, polyimide orpolyethylene naphthalate.

In the LED module 30, as shown in FIG. 2 , the LED elements 10 aremounted in a conductive state on the wiring part 22 via a solder layer23.

Regarding the size of the LED module 30, there is no special limitation;however, that having a diagonal length on the order of 50 to 200 inchesis preferable from the viewpoint of cost performance generally.Alternatively, as mentioned above, it is possible to configure the lightemitting surface of a self-luminous display such as the large-scalemicro LED display device 100, by connecting at plurality of the LEDmodules 30 for self-luminous displays in a matrix form on the sameplane. For example, it is also possible to connect LED modules 30 havinga 6 inches diagonal length in 100×100 length/width to configure a microLED television equipped with a large screen having a diagonal length of600 inches.

(LED Element)

The LED elements 10 constituting the LED module 30 for self-luminousdisplays by mounting to a wiring substrate 20 are light emittingelements using the light emission in a PN junction in which a P-typesemiconductor and N-type semiconductor are joined. A structure in whicha P-type electrode and N-type electrode are provided on the top andbottom surface of the element, and a structure in which both the P-typeand N-type electrodes are provided on one element surface have beenproposed. LED elements 10 of either structure can be used in the LEDdisplay device 100 of the first embodiment; however, it is possible topreferably use a micro-sized LED element such as the LED elementdisclosed as a “chip-type electronic component” in Japanese UnexaminedPatent Application, Publication No. 2006-339551. The LED elementdisclosed in the same document is said to have a size inwidth×depth×height of about 25 μm×15 μm×2.5 μm.

The LED element 10 preferably includes an LED light emitting chip 11,and a resin cover 12 which covers this. In addition, as this resin cover12, an organic insulating material such as epoxy resin, silicon resinand polyimide resin are used, and among these, epoxy resin is preferablyused. This is because the resin cover 12 formed by epoxy resin does notonly protect simply the LED light emitting chip 11 from physical impact,and also play a role of raising the light emitting efficiency of the LEDelement 10 by suppressing total reflection of light into thesemiconductor caused by the difference in refractive index between airand the semiconductor constituting the LED light emitting chip 11. Theencapsulant sheet 1 is preferably established as an encapsulant equippedto the micro LED display device 100, in the point of being formed bypolyolefins superior in adherence with the epoxy resin.

In the self-luminous display, it is possible to preferably use LEDelements made to include the LED light emitting chip and a resin covercoating this, having a size with the width and depth both being no morethan 300 μm, and height no more than 200 μm. In this case, thearrangement interval of these LED elements is preferably at least 0.03mm and no more than 100 mm.

In the self-luminous display, it is possible to preferably use an LEDelement made to include the LED light emitting chip and a resin covercoating this, having a very small size with the width and depth bothbeing no more than 50 μm, and height no more than 10 μm. In this case,the arrangement interval of these LED elements is preferably at least0.03 mm and no more than 100 mm. Such an implementation state of LEDelements is a typical implementation state of LED elements in a microLED television specifically.

(Encapsulant Sheet)

The encapsulant sheet of the first embodiment is a resin sheet which canbe preferably used as a resin sheet laminated on the wiring substrate bycovering a large number of micro light emitting elements in the“self-luminous display”. In addition, this encapsulant sheet is made asa sheet-like member, by forming the encapsulant composition withpolyolefin as the base resin. It should be noted that the encapsulantsheet of the first embodiment may be a single layer film; however, itmay be a multi-layer film configured by a core layer, and skin layersarranged on both sides of the core layer. It should be noted that themulti-layer film of the first embodiment refers to a film or sheetconsisting of a structure having at least any outermost layer,preferably a skin layer molded on both outermost layers, and a corelayer that is a layer other than the skin layer.

The thickness of this encapsulant sheet is sufficient so long as beingat least 50 μm and no more than 1000 μm, and is preferably at least 50μm and no more than 500 μm, and more preferably at least 50 μm and nomore than 300 μm. In addition, in the case of the LED element which isthe target for coating being an LED element of very small size having aheight of no more than 10 the thickness of the encapsulant sheet ispreferably at least 25 μm and no more than 100 μm. If the thickness ofthe encapsulant sheet is at least 50 μm, it is possible to sufficientlyprotect the LED element from external shock. On the other hand, if thethickness of the encapsulant sheet is no more than 1000 μm, it ispossible to exhibit sufficient molding property. More specifically, itis possible to perform favorable lamination without gaps by the resinconstituting the encapsulant sheet sufficiently wrapping around theunevenness of the LED module surface, during hot pressing in a statecovering the LED elements. In the self-luminous display afterintegration, it is possible to sufficiently ensure the lighttransmittance of the encapsulating layer consisting of the encapsulantsheet.

Then, in the encapsulant sheet of the first embodiment, the “meltviscosity measured at a temperature of 120° C. at a sheet rate of2.43×10 sec⁻¹” is at least 5.0×10³ poise and no more than 1.0×10⁵ poise,and preferably this melt viscosity is at least 7.0×10³ poise and no morethan 9.0×10⁴ poise, and more preferably at least 8.0×10⁴ poise and nomore than 9.0×10⁴ poise. It should be noted that the above-mentionedmelt viscosity of the first embodiment shall refer to the melt viscositymeasured by a method based on JIS K7199.

By setting the above-mentioned “melt viscosity” to at least 5.0×10³poise, it is possible to sufficiently suppress squeezing out of resincaused by excessive flow during hot pressing of the encapsulant sheet,or the occurrence of poor luminescence caused by lateral stress to theLED element, and moreover, possible to satisfactorily maintain theuniformity of the film thickness of the encapsulant sheet after theabove-mentioned hot pressing. In a self-luminous display such as themicro LED display device 100, a special uniformity in film thickness isdemanded in the encapsulant sheet layered on the light emitting side ofthe LED element. This is because, if the film thickness at the centralpart of this encapsulant sheet and the film thickness at the end parteven slightly differ, the encapsulant sheet becomes a lenticular state,and will have an unintended unpreferable effect on the display qualityof the micro LED display device.

On the other hand, by setting the above-mentioned “melt viscosity” to nomore than 1.0×10⁵ poise, it is possible to favorably retain the moldingproperty during hot pressing of the encapsulant sheet.

The melt viscosity measured at the temperature of 120° C. at the shearviscosity of 2.43×10 sec⁻¹, for example, can obtain the desired value,by selecting a polyolefin which is the base resin of the resin sheet, ora material other than the base resin contained in the encapsulantcomposition. As viewpoints upon selecting a polyolefin, for example, itis possible to exemplify the molecular structure, molecular weight anddensity of the polyolefin. As the molecular structure of the polyolefin,for example, according to the type of olefin and polymerization number,length of the straight chain portion, number and length of branchedportions, and type, number and length of side chain portions, it ispossible to adjust the value of the above-mentioned “melt viscosity”.More specifically, if lengthening the length of the straight chainportion, the value of the “melt viscosity” has a tendency of becomingsmaller, and if shortening the length of the straight chain portion, thevalue of the “melt viscosity” has a tendency of becoming larger. Ifincreasing the number of branched portions, the value of the “meltviscosity” has a tendency of becoming smaller, and if making the numberof branched portions smaller, the value of the “melt viscosity” has atendency of becoming larger. If introducing a polar group to the sidechain portion, the value of the “melt viscosity” has a tendency ofbecoming larger. If making the molecular weight of the polyolefinlarger, the value of the “melt viscosity” has a tendency of becominglarger, and if making the molecular weight of the polyolefin smaller,the value of the “melt viscosity” has a tendency of becoming smaller. Ifmaking the density of the polyolefin larger, the value of the “meltviscosity” has a tendency of becoming larger, and if making the densityof the polyolefin smaller, the value of the “melt viscosity” has atendency of becoming smaller. As an adjustment by materials other thanthe base resin contained in the encapsulant composition, for example, amethod of adding a resin having different “melt viscosity” than the baseresin, or a method of adding an inorganic component such as a filler canbe exemplified.

Conventionally, the value of MFR widely adopted as the indicator for thefluidity of the encapsulate sheet is a measurement at 190° C., in thecase of measuring based on JIS K6922. However, this temperature divergesfrom the temperature upon the encapsulant sheet for the self-luminousdisplay actually melting upon hot pressing. As shown in the Exampleslater, even if the value of the MFR is in the appropriate range ofvalues, in the case of the above-mentioned “melt viscosity” exceeding apredetermined value, the required molding property may not be securable.The reason thereof is surmised as the MFR being an evaluation of theflowability due to static load, and is an index assuming a liquid havinglow viscosity. By measurement of MFR, it is considered that measurementon the polyolefin at a temperature in the vicinity of 120° C. which is astate having constant viscosity cannot be appropriately performed, orevaluation on the viscosity cannot be appropriately performed. As anindex for controlling the fluidity of resin upon hot pressing, in placeof MFR, as described above, it is possible to obtain an index related toprecise resin selection with high effectiveness, adapted to the mode ofuse of the encapsulant sheet, by defining the shear modulus at atemperature of 120° C., i.e. melt viscosity at a shear rate of 2.43×10sec⁻¹ measured at a temperature of 120° C., as described above, as anindex for physical property optimization of the encapsulant sheet forself-luminous displays.

The melt viscosity measures the viscosity while melting. Since there isconcern over the encapsulant sheet for self-luminous displays, whenperforming hot pressing at a high temperature such that greatly exceeds120° C., damaging the LED module, it is used at a temperature in thevicinity of 120° C. The polyolefin has a constant viscosity at atemperature in the vicinity of 120° C. For the encapsulant sheet forself-luminous displays, since it is required to fill gaps between smallLED elements, it is considered important to focus on the viscosity ofthe encapsulant sheet.

The encapsulant sheet of the first embodiment has a Vicat softeningpoint preferably exceeding 60° C. and no more than 100° C., and morepreferably at least 70° C. and no more than 90° C. By letting the Vicatsoftening point of the encapsulant sheet exceed 60° C., it is possibleto more reliably suppress the occurrence of blocking in themanufacturing process of the self-luminous display using the encapsulantsheet, and contributes to an increase in the productivity of theself-luminous display. On the other hand, by setting the Vicat softeningpoint to no more than 100° C., it is possible to sufficiently maintainthe molding property on the order required in the encapsulant sheet forself-luminous displays.

Regarding the aforementioned Vicat softening point of the encapsulantsheet of the first embodiment, in more detail, it is preferable to morerigorously optimize according to the melting point of this encapsulantsheet. More specifically, in the case of the melting point of theencapsulant sheet being in a relatively low range of at least 50° C. andless than 70° C., in order to suppress excessive flow during hotpressing, it is preferable to set the Vicat softening point as a rangeof at least 60° C. and less than 70° C. In addition, a case of thismelting point being in a relatively high range of at least 70° C.favorably maintains the molding property during hot pressing; therefore,it is preferable to set the Vicat softening point as a range of at least70° C. and no more than 100° C. It should be noted that the “Vicatsoftening point” of the encapsulant sheet of the first embodiment shallbe considered a value obtained by measuring, based on ASTM D1525, theVicat softening point at a stage after sheet formation completion of theencapsulant sheet made by sheet forming the encapsulant compositioncontaining resin component and other additives by a molding method suchas melt extrusion molding.

From another viewpoint, the encapsulant sheet of the first embodimentpreferably has a Durometer A hardness of at least 60 and less than 95.If the Durometer A hardness of the encapsulant sheet is less than 60,the crystallization rate of the polyolefin slows, and the sheet drawnfrom the extruder is sticky. Peeling of the cooling roller therebybecomes difficult, and obtaining the encapsulant sheet becomesdifficult. In addition, due to sticking to the encapsulant sheetoccurring, blocking and feeding of the sheet become difficult. On theother hand, if the Durometer A hardness exceeds 95, the molding propertydeclines, and the following nature to the unevenness of the LED elementsbecomes insufficient.

The base resin of the encapsulant composition constituting theencapsulant sheet can be widely selected from thermoplastic polyolefins,so long as the “melt viscosity measured at a temperature of 120° C. at asheet rate of 2.43×10 sec⁻¹” is in the above-mentioned range.Thereamong, it is possible to preferably use a polyethylene such aslow-density polyethylene (LDPE), linear low-density polyethylene(LLDPE), or metallocene linear low-density polyethylene (M-LLDPE). Itshould be noted that “base resin” in the first embodiment shall refer toa resin, in a resin composition containing this base resin, having thelargest content ratio among the resin component of this resincomposition.

The density of the above-mentioned polyethylene used as the base resinin the encapsulant composition is sufficient so long as at least 0.870g/cm³ and no more than 0.910 g/cm³, and is preferably at least 0.895g/cm³ and no more than 0.905 g/cm³. By setting the density of the baseresin of the encapsulant composition to no more than 0.910 g/cm³, it ispossible to maintain the adherence to the wiring substrate of theencapsulant sheet in a preferable range. In addition, by setting thisdensity to at least 0.890 g/cm³, it is possible to impart sufficientheat resistance required to the encapsulant sheet without subjecting toa cross-linking treatment.

It is more preferable to contain a fixed amount in each encapsulantcomposition, as necessary, a silane copolymer (hereinafter referred toas silane-modified polyethylene) made by copolymerizing ethylene,ethylenically unsaturated silane compound as a comonomer, in theencapsulant composition. The silane-modified polyethylene, for example,is made by graft-polymerizing with the ethylenically unsaturated silanecompound as a side chain to the linear low-density polyethylene (LLDPE)serving as the main chain. Such a graft copolymer, due to the degree offreedom of the silanol group contributing to the adhesive strengthbecoming higher, can improve the adhesiveness of the encapsulant sheet 1to other members in a self-luminous display such as the micro LEDdisplay device 100. The content in the encapsulant composition of thissilane-modified polyethylene, for example, if a case of a multi-layerencapsulant sheet consisting of a configuration of skin layer-corelayer-skin layer, is preferably at least 2% by mass and no more than 20%by mass in the encapsulant composition for the core layer, and at least5% by mass and no more than 40% by mass in the encapsulant compositionfor the skin layers. At least 10% of the silane-modified polyethylene ismore preferably contained in the encapsulant composition for the skinlayers. It should be noted that the silane modification amount in theabove-mentioned silane-modified polyethylene is preferably on the orderof at least 1.0% by mass and no more than 3.0% by mass. The preferredcontent range of the silane-modified polyethylene in the above-mentionedencapsulant composition is premised on the above-mentioned silanemodification amount being within this range, and it is desired toappropriately fine tune according to the fluctuation in thismodification amount.

By using the silane-modified polyethylene as a component of theencapsulant composition for self-luminous displays, it is possible toproduce a self-luminous display superior in strength, durability, etc.,and superior in weather resistance, heat resistance, water resistance,light resistance, wind pressure resistance, hail resistance, and otherproperties, and further having superior heat fusion without beinginfluenced by the production conditions such as thermal pressure bondingto produce the self-luminous display, and suited to various applicationsstably and at low cost.

Second Embodiment Encompassed by Present Embodiment

More specifically, the second embodiment provides the following.

A sixteenth aspect of the present invention is an encapsulant sheet fora self-luminous display or for a direct backlight which is asingle-layer or a multi-layer resin sheet that includes an adhesivelayer exposed on a topmost surface, in which the adhesive layer containsa resin component and a silane component, in which the resin componentincludes a polyolefin, in which content of the silane component relativeto resin component of the adhesive layer is at least 0.02% by mass andno more than 0.15% by mass.

The sixteenth aspect of the present invention establishes the base resinin the encapsulant sheet encapsulating an electronic device having afine unevenness as a thermoplastic polyolefin, and moreover, containsthe silane component in a state in which the majority of the silanecomponent is graft-polymerized to this polyolefin in a specific range ofcontent. It is thereby possible to obtain an encapsulant sheet combininga balance of adhesion durability to a circuit board during use of themicro LED television, etc. which is the final product, and reworkabilityin a manufacturing stage process.

According to a seventeenth aspect of the present invention, in theencapsulant sheet as described in the sixteenth aspect, the polyolefinis a polyethylene having a density of at least 0.870 g/cm³ and no morethan 0.910 g/cm³.

According to the seventeenth aspect of the present invention, it ispossible to establish an encapsulant sheet having favorable adhesivenessand heat resistance.

According to an eighteenth aspect of the present invention, the silanecomponent includes a graft silane component which graft-polymerizes tothe polyolefin of the adhesive layer, in which the adhesive layercontains at least 70% by mass and no more than 100% by mass of the graftsilane component with respect to the silane component.

According to the eighteenth aspect of the present invention, it ispossible to more reliably acquire the above-mentioned effects which canbe exerted by the invention of the sixteenth or seventeenth aspect, in aproduct life cycle from manufacture to use of a general micro LEDtelevision. In particular, it is possible to significantly improve thestability of the product quality of the encapsulant sheet frommanufacturing completion of the encapsulant sheet until incorporatedinto the final product.

According to a nineteenth aspect of the present invention, in theencapsulant sheet as described in any one of the sixteenth to eighteenthaspects, the encapsulant sheet is a multi-layer resin sheet in which theadhesive layer is laminated to a base layer with polyethylene as a baseresin.

According to the nineteenth aspect of the present invention, theencapsulant sheet as described in any one of the sixteenth to eighteenthaspects is established as a resin sheet of multi-layer configurationfurther including a base layer in addition to the adhesive layer. Byconfiguring the base layer by a resin more superior in heat resistance,it is possible to establish as an encapsulant sheet superior in otherphysical properties such as heat resistance, while securing each effectwhich can be exerted by any one of the sixteenth to eighteenth aspectsof the present invention in the adhesive layer.

A twentieth aspect of the present invention is a production method of anencapsulant sheet for a self-luminous display or a direct backlight, inwhich the encapsulant sheet is a single-layer or a multi-layer resinsheet configured to contain an adhesive layer exposed at a topmostsurface, the method comprising: an adhesive layer forming step offorming the adhesive layer by melt forming an encapsulant compositionfor adhesive layer, in which the encapsulant composition for adhesivelayer contains polyolefin and a silane component, and is free ofcross-linking agent, at least 70% by mass and no more than 100% by massof silane component among the silane component is a graft silanecomponent which is graft-polymerizing to the polyolefin, and content ofthe silane component relative to the polyolefin is adjusted so that afirst adhesive strength measured by a first adhesion test of theadhesive layer is at least 3.0 N/15 mm and no more than 8.0 N/15 mm, anda second adhesive strength measured by a second adhesion test of theadhesive layer is at least 10.0 N/15 mm and no more than 20.0 N/15 mm.The first adhesion test measures the first adhesive strength by adheringan encapsulant sheet sample cut to a width of 15 mm onto a glass epoxyplate (75 mm×50 mm×0.05 mm) and performing lamination processing in avacuum heated laminator at 140° C. for 10 minutes, and performing avertical peeling (50 mm/min) test with a peel tester on the encapsulantsheet sample adhered on the glass epoxy plate. The second adhesion testmeasures the second adhesive strength by adhering an encapsulant sheetsample cut to a width of 15 mm onto a glass epoxy plate (75 mm×50mm×0.05 mm) and performing lamination processing in a vacuum heatedlaminator at 140° C. for 10 minutes, thereafter further performingcuring processing in a vacuum heated laminator at 150° C. for 15minutes, and performing a vertical peeling (50 mm/min) test with a peeltester on the encapsulant sheet sample adhered on the glass epoxy plate.

The twentieth aspect of the present invention defines the technicalconcept according to the sixteenth aspect of the present invention as aproduction method. This production method is a method of establishingthe base resin in the encapsulant sheet encapsulating an electronicdevice as a thermoplastic polyolefin, and moreover, using component inwhich the majority of the silane component is graft-polymerized to thepolyolefin, and then optimizing the content of silane component so thatthe adhesiveness in a plurality of stages at the manufacturing stage canbe optimized. It is thereby possible to obtain an encapsulant sheetcombining a balance of adhesion durability to a circuit board during useof the micro LED television, etc. which is the final product, andreworkability in a manufacturing stage process.

A twenty-first aspect of the present invention is a self-luminousdisplay comprising: the encapsulant sheet as described in any one of thesixteenth to nineteenth aspects; a display panel; and a light emittingmodule in which a plurality of light emitting elements are mounted to awiring substrate, in which the encapsulant sheet is laminated to thelight emitting module to cover the light emitting elements and thewiring substrate, and the display panel is laminated to the encapsulantsheet.

The twenty-first aspect of the present invention is an application ofthe second embodiment to various LED display devices of which a microLED television expected as mainstream of next generation monitors isrepresentative. It is thereby possible to obtain an LED display devicesuperior in productivity and durability.

According to a twenty-second aspect of the present invention, in theself-luminous display as described in the twenty-first aspect, the lightemitting element is an LED element, the LED element has an LED lightemitting chip and a resin cover which covers the LED light emittingchip, width and depth of the LED element are both no more than 300 μm,and height is no more than 200 μm, and an arrangement interval of eachof the LED elements is at least 0.03 mm and no more than 100 mm.

The twenty-second aspect of the present invention is applying theself-luminous display of the twenty-first aspect to a high-definitiondot-matrix display device or the like, made by densely mounting LEDelements in a chip-on-board format directly mounting many LED chips onthe board. It is thereby possible to obtain a high-definition LEDdisplay device superior in productivity and durability.

According to a twenty-third aspect of the present invention, in theself-luminous display as described in the twenty-second aspect, widthand depth of the LED element are both no more than 50 μm, and height isno more than 10 μm, and an arrangement interval of each of the LEDelements is at least 0.05 mm and no more than 5 mm.

The twenty-third aspect of the present invention is applying theself-luminous display of the twenty-second aspect to a “micro LEDtelevision” for which development has advanced in recent years and isexpected as a next generation video display device. It is therebypossible to obtain an ultrahigh-definition LED display device superiorin productivity and durability.

A twenty-fourth aspect of the present invention is a reworking method ofthe self-luminous display as described in any one of the twenty-first totwenty-third aspects, the method comprising: sequentially performing athermal lamination step divided into two stages of processing of aninitial lamination processing and final curing processing to integrate alaminate body including a light emitting module and an encapsulant sheetlaminated to cover light emitting elements configuring the lightemitting module; and performing a reworking step accompanying anoperation to cut out a part of the encapsulant sheet and peel from thelight emitting module, after completion of the initial laminationprocessing and before start of the final curing processing.

The twenty-fourth aspect of the present invention can achieve atpreferable levels both adhesion durability during long term use as aself-luminous display such as a micro LED television, and reworkabilityin the manufacturing stage process, for an LED module for self-luminousdisplays configured using the encapsulant sheet as described in thesixteenth aspect, for example.

According to the second embodiment, it is possible to provide anencapsulant sheet for self-luminous displays which possesses bothadhesion durability during long term use as a self-luminous display suchas a micro LED television, and reworkability in the production stage.

In the self-luminous display, an encapsulant sheet for protecting thelight emitting element is laminated on the surface on the light emittingside of the LED module (light emitting module) configured by lightemitting elements such as LED elements being mounted to a wiringsubstrate (refer to Patent Documents 2 and 3). The encapsulantcontaining the polyethylene is disclosed in Patent Document 2, and anencapsulant containing an acid-modified polyethylene which is moresuperior in glass adhesion is disclosed in Patent Document 3.

The adhesion durability over a long term with the circuit boardconsisting of glass epoxy resin, glass plate or the like, afterintegration as the aforementioned micro LED television or the like isdemanded in the encapsulant sheet for self-luminous displays during usethereof. However, on the other hand, for example, in the above-mentionedmicro LED television, although several tens of thousands to severalhundreds of thousands of LED elements are mounted per one unit, it isvirtually impossible to completely prevent, at the initial stage ofmounting, poor light emission of all of these LED elements. Based onthis, “reworkability” in a state laminated and integrated to the circuitboard on which LED elements are mounted is also demanded in theencapsulant sheet for self-luminous displays.

It should be noted that “rework” in the second embodiment shall refer toan operation of cutting part of the encapsulant sheet without damagingnormal LED elements, peeling off from the circuit board, and replacingonly part of the defective elements among the LED elements mounted tothe circuit board. In addition, “reworkability” shall refer to thecompliance of the above-mentioned operation of “rework” of theencapsulant sheet, i.e. appropriate peeling ease during this operation.

The second embodiment has been made taking account of the above suchsituation, and has an object of providing an encapsulant sheet forself-luminous displays which possesses both adhesion durability duringlong term use as a self-luminous display such as a micro LED television,and reworkability in the production stage.

The present inventors thoroughly researched, a result of which foundthat the above-mentioned problem could be solved by optimizing thesilane component graft-polymerized to the polyolefin in an encapsulantsheet for electronic devices which is a resin sheet with a thermoplasticpolyolefin as the base resin, thereby arriving at completing the secondembodiment. Hereinafter, a second embodiment will be explained morespecifically.

It should be noted that, due to being shared with the first embodiment,explanations of the self-luminous display, micro LED display device, LEDmodule and LED element will be omitted.

(Encapsulant Sheet)

The encapsulant sheet of the second embodiment is a resin sheet whichcan preferably be used as a resin sheet laminated on the wiringsubstrate by covering the light emitting elements in a “self-luminousdisplay”, etc. on which a large number of micro light emitting elements,such as micro LED television, and is a resin sheet superior inreworkability.

The encapsulant sheet of the second embodiment is a sheet made as amember of sheet form, by forming the encapsulant composition withpolyolefin as the base resin into a film. Then, in this sheet-likestate, it is a single-layer or a multi-layer resin sheet configured tocontain an adhesive layer exposed on the topmost surface. In otherwords, the encapsulant sheet of the second embodiment may be a singlelayer sheet consisting of only the adhesive layer explained in detailbelow. Alternatively, the encapsulant sheet of the second embodiment maybe a multi-layer sheet made by an adhesive layer and another resin layerhaving a different resin density and composition than the adhesive layerbeing laminated. It should be noted that the multi-layer film of thesecond embodiment refers to a film or sheet consisting of a structurehaving an adhesive layer formed on at least either outermost layer,preferably both outermost layers, and a base layer which is a layerother than the adhesive layer.

In the case of the encapsulant sheet of the second embodiment being amulti-layer sheet, it is possible to exemplify a layer configurationmade by an adhesive layer containing a silane component consisting ofpolyolefin on at least one surface, preferably both surfaces, of thebase layer consisting of polyolefin as a preferred example of the layerconfiguration, for example. In this case, as the polyolefin constitutingthe base layer, it is preferable to select a resin more superior in heatresistance than the polyolefin constituting the adhesive layer.

Either way, with the encapsulant sheet of the second embodiment, even ina case of being any layer configuration other than the layerconfiguration exemplified in the above description, it is made anessential requirement for the layer of the topmost surface exposed on atleast one surface of the resin sheet to be the aforementioned adhesivelayer.

In the case of the encapsulant sheet of the second embodiment being aresin sheet of a single layer consisting of only the adhesive layer, thetotal thickness thereof may be at least 50 μm and no more than 1000 μm,is preferably at least 50 μm and no more than 500 μm, and morepreferably at least 50 μm and no more than 300 μm. In addition, in thecase of the encapsulant sheet 1 being a multi-layer resin sheet of threelayers of two types consisting of a base layer and adhesive layerslaminated on both sides thereof, the total thickness thereof ispreferably at least 70 μm and no more than 500 μm, and the thickness ofthe adhesive layer in this case is preferably at least 10 μm and no morethan 100 μm, and the thickness of the base layer is preferably at least50 μm and no more than 300 μm.

However, in the case of the LED element which is the target for coatingbeing a very small-sized LED element having a height no more than 10 μm,even in the case of the total thickness of the encapsulant sheet beingany layer configuration, it is preferable for the total thickness to beat least 25 μm and no more than 100 μm, and in the case of being amulti-layer sheet of three layers of two types, the thickness of anadhesive layer within the above-mentioned total thickness layer ispreferably at least 5 μm and no more than 30 μm.

Depending on the size of the LED element which is the coating target, bythe total thickness of the encapsulant sheet being at least 50 μm, or atleast 5 μm, it is possible to sufficiently protect the LED element fromexternal impact. On the other hand, if the thickness of the encapsulantsheet is no more than 1000 μm, it will tend to exhibit a moldingproperty during hot pressing in the thermal laminating process. Morespecifically, during the hot pressing in the state of coating the LEDelement, it tends to carry out favorable lamination without gaps by theresin constituting the encapsulant sheet sufficiently wrapping aroundthe surface irregularities of the LED module surface. In addition, inthe case of the LED element which is the target of coating being a verysmall-sized LED element having a height no more than 10 μm, if thethickness of the encapsulant sheet is no more than 100 μm, in theself-luminous display after integration, the light transmittance of theencapsulation layer consisting of the encapsulant sheet tends to bemaintained at a favorable level.

In the second embodiment, as the polyolefin establishing the adhesivelayer of the encapsulant sheet of a single layer or an encapsulant sheetof multiple layers, the polyolefin can preferably use a polyolefinhaving a density of at least 0.870 g/cm³ and no more than 0.910 g/cm³.In addition, it is possible to more preferably use a low-densitypolyethylene having a density of at least 0.895 g/cm³ and no more than0.905 g/cm³. By setting the density of the base resin which is theadhesive layer as no more than 0.910 g/cm³, it is possible to maintainthe adhesiveness to the wiring substrate, etc. of the encapsulant sheetto the preferred range. In addition, by setting this density as at least0.870 g/cm³ a, it is possible to impart the heat resistance required inthe encapsulant sheet without subjecting to a cross-linking treatment.It should be noted that “base resin” in the second embodiment shallrefer to a resin, in a resin composition containing this base resin,having the largest content ratio among the resin component of this resincomposition.

As the above-mentioned polyethylene serving as the base resin of theencapsulant composition for the adhesive layer, in more detail, it ispossible to preferably use low-density polyethylene (LDPE), linearlow-density polyethylene (LLDPE) or metallocene linear low-densitypolyethylene (M-LLDPE). Thereamong, M-LLDPE which is synthesized usingmetallocene catalyst which is a single-site catalyst has few branches ofside chains, and uniform distribution of comonomer; therefore, by themolecular weight distribution being narrow, and being easy to makeultra-low density, it is possible to establish the adhesiveness of theencapsulant sheet 1 relative to the wiring substrate 20 consisting ofglass epoxy resin plate, glass plate or the like in the self-luminousdisplay such as the micro LED display device 100 to be more superior.

Then, in the adhesive layer constituting the encapsulant sheet, a silanecomponent is contained within a specific content range in the polyolefinwhich is the base resin, and preferably in the aforementionedpolyethylene. The content of “silane component” in the resin componentof the adhesive layer is sufficient so long as at least 0.02% by massand no more than 0.15% by mass, and is preferably at least 0.03% by massand no more than 0.10% by mass. If the amount of silane component in theresin component of the adhesive layer is 0.02% by mass, the initialadhesiveness in the production process of integration of theself-luminous display tends to be insufficient. On the other hand, inthe case of this amount exceeding no more than 0.15% by mass, thereworkability of this production process will be insufficient. Inaddition, in this case, deterioration of the silane component duringstorage tends to occur, and there is also a tendency of the tensilestrength of the encapsulant sheet and the heat fusion declining.

In the encapsulant sheet of the second embodiment, the majority of this“silane component” contained in the adhesive sheet, i.e. at least 70% bymass and no more than 100% by mass of silane component in this silanecomponent, is a “graft silane component” which is graft-polymerizing tothe polyolefin that is the base resin, and the proportion of “unreactedsilane component” not graft-polymerizing to the same base resin in thissilane component is preferably no more than 30% by mass. By theproportion of “graft silane component” in the silane component being atleast 70% by mass, i.e. the above proportion of “unreacted silanecomponent” being no more than 30% by mass, it is possible to lengthenthe use expiration date (shelf life) of the encapsulant sheet forself-luminous displays. More specifically, in the case of the aboveproportion of this “unreacted silane component” exceeding 30% by mass,the use expiration date (shelf life) upon storing in an environment at23° C. and 50%, i.e. the period for which the adhesiveness retentionrate between the encapsulant sheet and glass epoxy substrate immediatelyafter film formation is at least 80%, is on the order of 3 to 6 months;whereas, by suppressing this proportion to less than 30% by mass, itbecomes possible to make this period 12 to 18 months.

Herein, “silane component” in the second embodiment shall refer to“alkoxysilane grafted to main chain of base resin and alkoxysilane notgrafted”. In addition, “graft silane component” in the second embodimentshall refer to “alkoxy silane component graft-polymerizing to the baseresin”, and “unreacted graft component” which is another silanecomponent shall refer to “free alkoxysilane component not grafted tobase resin”.

It should be noted that, regarding the content (% by mass”) of the“graft silane component” of the encapsulant sheet, it is possible tomeasure the content thereof by quantifying the Si atomic weight in ICPemission spectral analysis or EPMA, and qualifying the alkoxysilanesgrafted by gas chromatography. It should be noted that the “unreactedsilane component”, i.e. free alkoxysilane component in the base resin,for example, can be extracted by immersing in a solvent such as toluene,and after extraction, it is possible to quantify similarly by the aboverespective analysis methods, other than ICP emission spectral analysis.

As the material of the “graft silane component” in the adhesive layer,it is possible to use a silane-modified polyolefin, and preferably touse a silane-modified polyethylene. This silane-modified polyethylene ismade by graft-polymerizing an ethylenically unsaturated silane compoundas a side chain to a linear low-density polyethylene (LLDPE), etc.serving as the main chain, for example. Such a graft copolymer has ahigher degree of freedom of the silanol groups contributing to theadhesive strength. It is thereby possible to improve the adhesivenessand adhesion durability of the glass epoxy substrate, etc. which is theencapsulant sheet 1 to the wiring substrate 20. The silane-modifiedpolyethylene can be produced by the method disclosed in JapaneseUnexamined Patent Application, Publication No. 2003-46105, for example.

As the resin material forming the adhesive layer, in the case of usingthis silane-modified polyethylene, the graft amount of ethylenicallyunsaturated silane compound of this silane-modified polyethylene, andthe added amount of this silane-modified polyethylene relative to thetotal resin component of the adhesive layer may be appropriatelyadjusted so that the amount of silane compound in the resin component ofthe adhesive layer becomes in the aforementioned range of at least 0.02%by mass and no more than 0.15% by mass.

Adjustment of this graft amount and added amount are as described belowin detail. In the case of obtaining silane-modified polyethylene bygraft-polymerizing vinyl trimethoxysilane, which is ethylenicallyunsaturated silane compound, with the base resin such as a linearlow-density polyethylene (LLDPE), since the molecular weight of vinyltrimethoxysilane is 148.2; whereas, the molecular weight of Si is 28.1,the proportion of Si in vinyl trimethoxysilane is on the order of 19.0%,whereby the silane component amount among the 5.0 parts by mass of thevinyl trimethoxysilane is on the order of 0.95 parts by mass, forexample. In addition, since the silane components volatilizing into theatmosphere during the course of production of the encapsulant sheet areabundant, in the case adding 5.0 parts by mass of vinyltrimethoxysilane, the silane component finally remaining in the resincomponent of the encapsulant sheet becomes on the order of 0.4 parts bymass generally. It should be noted that, by using silane-modifiedpolyethylene without separate addition such as a silane coupling agent,it is possible to set approximately 80% to 99% as the graft silanecomponent in the overall silane component in the resin. Regarding thegraft amount of the silane component and added amount of polymerizedresin during production of the aforementioned silane-modifiedpolyethylene, based on the above items as general references, it ispreferable to optimize the final formulation according to the conditionsof each manufacturing site.

The MFR of the polyolefin serving as the base resin of the adhesivelayer is preferably at least 5 g/10 min and no more than 35 g/10 min. Bythe MFR being in the range of at least 5 g/10 min and no more than 35g/10 min, it is possible to improve the initial adhesiveness andadhesion durability with balance. It should be noted that the melt massflow rate (MFR) of the second embodiment, unless otherwise noted, shallrefer to the value of the melt mass flow rate (MFR) at 190° C., load of2.16 kg measured according to JIS K6922-2, as mentioned above.

For example, as in the encapsulant sheet 1 shown in FIG. 4 , in the caseof the encapsulant sheet in the second embodiment being a multi-layersheet, although it is preferable for the base resin of the base layer touse the same polyolefin as the adhesive layer, it is preferable toselect a resin which is more superior in heat resistance than thepolyolefin constituting the adhesive layer. More specifically, it ispreferable to use a polyethylene having a density of at least 0.890g/cm³ and no more than 0.925 g/cm³, and it is more preferable to use apolyethylene having a density of at least 0.895 g/cm³ and no more than0.920 g/cm³. By setting the density of the base resin of the base layeras no more than 0.920 g/cm³, it is possible to retain the adhesivenessof the encapsulant sheet to the wiring substrate or the like within thepreferred range. In addition, by setting this density as at least 0.895g/cm³, it is possible to impart the heat resistance required in theencapsulant sheet 1, without subjecting to a cross-linking treatment.

In the encapsulant sheet 1 which is a multi-layer sheet, it is morepreferable to use a polyethylene or other polyolefin having a meltingpoint on the order of at least 80° C. and no more than 125° C. as thebase layer, and higher melting point than the silane-modified polyolefinforming the adhesive layer. In this case, by configuring the multi-layersheet by combining a resin of silane-modified polyethylene base of lowmelting point having a melting point on the order of 60 to 100° C. asthe silane-modified polyolefin forming the adhesive layer, it ispossible to establish an encapsulant sheet superior in balance of theheat resistance and adhesiveness, and adhesion durability.

In the encapsulant sheet 1 which is a multi-layer sheet, the containinga silane component in the base layer is not essential. However, in theresin component of the base layer, it may be contained in a proportionno more than 0.06% by mass. In addition, at least 70% of the silanecomponent among all silane components in this case is preferably theaforementioned “graft silane component”.

The encapsulant sheet of the second embodiment explained above is athermoplastic resin sheet with the aforementioned polyolefin as the baseresin, and not containing a crosslinker. In addition, the gel fractionof this encapsulant sheet is 0%. It should be noted that “gel fraction(%) in the second embodiment is a value obtained by placing 1.0 g ofencapsulant sheet on a resin mesh, extracting for 12 hours in xylene110° C., followed by removing the entire resin mesh and weighing beforeand after a drying process, carrying out a mass comparison from beforeand after extraction to measure the mass % of residual insolublefraction, and defining this as the gel fraction. It should be noted thatgel fraction 0% refers to a state in which the above-mentioned residualinsoluble fraction is substantially 0, and the crosslinking reaction ofthe encapsulant composition or encapsulant sheet has not substantiallystarted. More specifically, “gel fraction 0%” shall refer to a case ofthe above-mentioned residual insoluble fraction being entirelynonexistent, and a case of the mass % of the above-mentioned residualinsoluble fraction measured by precision balance being less than 0.05%by mass. It should be noted that a pigment component, etc. other thanresin component shall not be contained in the above-mentioned residualinsoluble fraction. In the case of contaminants other than these resincomponents mixing with the residual insoluble fraction by the abovetests, for example, by separately measuring the content in the resincomponent of these contaminants in advance, it is possible to calculatethe gel fraction which should be originally obtained for the residualinsoluble fraction derived from the resin component excluding thesecontaminants.

(Production Method of Encapsulant Sheet)

The encapsulant sheet of the second embodiment can be produced bysubjecting the encapsulant composition for forming each layer at leastincluding the adhesive layer for which the composition details weredescribed above, to the film formation step of melt forming into a sheetform. This melt formation can be carried out by a formation methodnormally used for usual thermoplastic resins, i.e. various formationmethods such as injection molding, extrusion molding, vacuum molding,compression molding and rotary molding. As the formation method of amulti-layer sheet, as one example, a molding method by coextrusion by atleast two types of melt kneading extruders, or a method of joining bydry laminating after film forming separately each layer can beexemplified.

It should be noted that in the encapsulant sheet of the secondembodiment, a crosslinker is often not contained in the encapsulantcomposition. For this reason, under the usual molding temperature oflow-density polyolefin, for example, heating conditions at around 120°C., a change in gel fraction is not realized, and the gel fraction ofthe encapsulant composition during film production is maintained at 0%.Consequently, it is possible to reduce the load acting on the extruderor the like during film production, and raise the productivity of theencapsulant sheet.

In particular, in the adhesive layer forming step of forming theadhesive layer using the encapsulant composition for the adhesive layer,the content of silane component in the polyolefin as the base resin ofthe encapsulant composition for the adhesive layer is found topreferably be in the range of at least 0.02% by mass and no more than0.15% by mass; however, it is more preferable to obtain a test filmforming step which determines an optimal value for the optimal contentof silane component relative to the polyolefin, so that the firstadhesive strength measured by the following first adhesion test of theadhesive layer becomes at least 3.0 N/15 mm and no more than 8.0 N/15mm, and the second adhesive strength measured by the following secondadhesion test of the adhesive layer becomes at least 10.0 N/15 mm and nomore than 20.0 N/15 mm. For example, the measurement result of each ofthe above-mentioned adhesive strengths of the sample encapsulant sheetobtained in this test film production step is fed back to the adjustmentof the silane component amount in the adhesive layer, a result of whichit is possible to favorably retain the reworkability of the encapsulantsheet, by continuing production using the encapsulant composition of thesame composition.

(First Adhesion Test):

Lamination processing was performed in a vacuum heated laminator at 140°C. for 10 minutes by adhering the encapsulant sheet sample cut to thesize of 75×50 mm on a glass epoxy plate (75 mm×50 mm×0.05 mm), and in astate penetrating to immediately above the glass epoxy plate surfacewith 15 mm width in the encapsulant sheet sample adhered on the glassepoxy plate, making a cut serving as the start for the peeling startlocation, and then performing a vertical peeling (50 mm/min) test with apeel testing machine (Tensilon universal testing machine RTF-1150-H) tomeasure a first adhesive strength.

(Second Adhesion Test)

Lamination processing was performed in a vacuum heated laminator at 140°C. for 10 minutes by adhering the encapsulant sheet sample cut to thesize of 75×50 mm on a glass epoxy plate (75 mm×50 mm×0.05 mm), andsubsequently, curing processing was further performed in the vacuumheated laminator at 150° C. for 15 minutes, and in a state penetratingto immediately above the glass epoxy plate surface with 15 mm width inthe encapsulant sheet sample adhered on the glass epoxy plate, making acut serving as the start for the peeling start location, and thenperforming a vertical peeling (50 mm/min) test with a peel testingmachine (Tensilon universal testing machine RTF-1150-H) to measure asecond adhesive strength.

(Production Method of Micro LED Display Device)

The micro LED display device 100 can be obtained by subjecting to a stepestablishing a laminate body made by laminating the LED module 30 forself-luminous displays made by LED elements 10 being mounted on thewiring substrate 20, the encapsulant sheet 1, and another optical memberarranged as necessary, and integrating this laminate body by hotpressing, and subsequently, further laminating and integrating thedisplay panel 2 to this laminate by adhering, pasting, or the like.

The above-mentioned thermal lamination process is preferably dividedinto the two stages processing of an initial lamination processing andfinal curing processing, which are sequentially performed. This isbecause, by performing the thermal lamination process by dividing intothe initial lamination processing of causing the encapsulant sheet tofollow the uneven surface of the LED without producing bubbles, andadhering, and the final curing processing of further increasing theadhesion after adhering to make an article with stable adhesion, itbecomes possible to produce encapsulant of micro LEDs of strongeradhesion under high quality stability.

As necessary, part of the laminated members may be joined by adhesive inadvance before the above-mentioned thermal lamination process. Theencapsulant sheet 1 of the second embodiment is characterized in thepoint of being a sheet which, during hot pressing in the thermallamination process for integration as this final product, exhibitssufficient molding property to impart reworkability contributing to aproductivity improvement, and superior in adhesion durability after thisthermal lamination process.

(Reworking Method of Micro LED Display Device)

Upon performing the production method of the above-mentioned micro LEDdisplay device, it is possible to perform the reworking step of cuttingpart of the encapsulant sheet 1 and peeling off from the LED moduleafter completion of the above-mentioned initial lamination processingand before start of the final curing processing, and then replacing LEDelements causing light emission deficiency, with ease. As mentionedabove, this is because the encapsulant sheet 1 is a sheet which realizesadhesion of a reworkable extent based on the above-mentioned firstadhesive strength after completion of the initial lamination processing,and realizes favorable adhesion durability based on the above-mentionedsecond adhesive strength after completion of the final curingprocessing.

Third Embodiment Encompassed by Present Embodiment

More specifically, the third embodiment provides the following.

A twenty-fifth aspect of the present invention is an encapsulant sheetfor a self-luminous display or a direct backlight, in which one surfaceis an adhesive surface, and the other surface is a peeling surface,adhesive strength of the adhesive surface measured by an adhesion testis at least 5.0 N/15 mm and no more than 50.0 N/15 mm, and adhesivestrength of the peeling surface is at least 0.1 N/15 mm and no more than3.0 N/15 mm. The adhesion test measures adhesive strength of eachsurface by adhering a surface on a side serving as a measurement targetof an encapsulant sheet sample cut to a width of 15 mm onto a blue-sheetglass plate (75 mm×50 mm×3 mm) and performing laminate treatment in avacuum heated laminator at 140° C. for 10 minutes, and performing avertical peeling (50 mm/min) test with a peel tester on the encapsulantsheet sample adhered on the blue-sheet glass plate.

In the twenty-fifth aspect of the present invention, the encapsulant forself-luminous displays is established as a resin film having anasymmetrical layer configuration of different adhesive strengths, at onesurface (adhesive surface) and another surface (peeling surface). It isthereby possible to obtain an encapsulant sheet combining adhesivenessto the circuit board surface having fine unevenness, and releasabilityfrom a heated plate on which placed during thermal laminationprocessing, and possible to produce LED modules for self-luminousdisplays with higher productivity, while keeping quality which is atleast equal to conventional, even without using a mold release film.

According to the twenty-sixth aspect of the present invention, in theencapsulant sheet as described in the twenty-fifth aspect, apolyethylene having a density of at least 0.870 g/cm³ and no more than0.930 g/cm³ is the base resin.

According to the twenty-sixth aspect of the present invention, it ispossible to optimize the balance between adhesiveness and moldreleasability of the encapsulant sheet.

According to a twenty-seventh aspect of the present invention, in theencapsulant sheet as described in the twenty-fifth or twenty-sixthaspect, the encapsulant sheet is a multi-layer resin sheet having anadhesive layer exposed at a surface on a side of the adhesive surface,and a non-adhesive layer exposed at a surface on a side of the peelingsurface, the adhesive layer contains a silane component in a proportionof at least 0.02% by mass and no more than 0.19% by mass relative toresin component, and the non-adhesive layer does not contain the silanecomponent, or even in a case of containing silane component, contentthereof relative to resin component is less than 0.02% by mass.

According to the twenty-seventh aspect of the present invention, asuitable amount of silane component is contained in the adhesive layerforming the adhesive surface, and silane component is either notcontained in the non-adhesive layer forming the peeling surface, or evenif contained, is limited to less than a very small amount. It is therebypossible to control the adhesive strength of each layer to a favorablerange, and more reliably acquire the above effects which can be exertedby the twenty-fifth or twenty-sixth aspect of the present invention.

According to a twenty-eighth aspect of the present invention, in theencapsulant sheet as described in any one of the twenty-fifth totwenty-seventh aspect, the encapsulant sheet is a multi-layer resinsheet in which the adhesive layer is laminated on one surface of a baselayer with polyethylene as a base resin, and the non-adhesive layer islaminated on the other surface thereof.

According to the twenty-eighth aspect of the present invention, theencapsulant sheet as described in any one of the twenty-fifth totwenty-seventh aspects is established as a resin sheet of three-layerconfiguration made by the adhesive layer and non-adhesive layerrespectively being laminated to both surfaces of the base layer.According to this, it is possible to easily produce an encapsulant sheetfor which the adhesive strength of each layer is controlledappropriately, by coextruding of resin compositions having respectivelydifferent contents of adhesive component, and possible to furtherestablish as an encapsulant sheet superior in productivity, whilesecuring the respective effects which can be exerted by the any one ofthe twenty-fifth to twenty-seventh aspects of the present invention.

A twenty-ninth aspect of the present invention is an LED module forself-luminous display comprising: the encapsulant sheet as described inany one of the twenty-fifth to twenty-eighth aspects; a light emittingmodule in which a plurality of light emitting elements is mounted on awiring substrate, in which the encapsulant sheet is laminated to thelight emitting module in a state opposing the adhesive surface againstthe light emitting element and the wiring substrate.

The twenty-ninth aspect of the present invention is applied to an “LEDmodule” which can be preferably used in order to configure aself-luminous display such as a “micro LED television” for whichdevelopment has advanced in recent years and is expected as a nextgeneration video display device. It is thereby possible to establish amodule superior in productivity and durability of a self-luminousdisplay made using this.

A thirtieth aspect of the present invention is a self-luminous displaycomprising: the LED module for self-luminous displays as described inthe twenty-ninth aspect; and a display panel, in which the display panelis laminated to the peeling surface of the encapsulant sheet configuringthe LED module.

The thirtieth aspect of the present invention is applying the LED moduleof the twenty-ninth aspect to the self-luminous display such as a “microLED television” for which development has advanced in recent years andis expected as a next generation video display device. It is therebypossible to obtain an LED display device superior in productivity anddurability.

A thirty-first aspect of the present invention is a product method ofthe LED module for self-luminous displays as described in thetwenty-ninth aspect, comprising: a thermal lamination step ofintegrating a laminate body in which the light emitting module and theencapsulant sheet are laminated, by thermal press bonding in a stateplacing on a heated plate including metal and/or glass, in which thethermal press bonding is performed by directly placing the peelingsurface of the encapsulant sheet configuring the laminate body on theheated plate, without going through a mold release film.

The thirty-first aspect of the present invention defines the technicalconcept according to the twenty-fifth aspect of the present invention asa production method. This production method can produce the LED modulefor self-luminous displays with higher productivity, while keepingquality which is at least equal to conventional, even without using amold release film, by using the encapsulant sheet combining adhesivenessto the circuit board surface having fine unevenness, and moldreleasability from a heated plate on which placed during thermallamination processing.

According to the third embodiment, it is possible to provide anencapsulant sheet for self-luminous displays which can produce an LEDmodule for self-luminous displays with higher productivity, whilekeeping quality at least equal to conventional, even without using amold release film.

The self-luminous display is a configuration in which a display panelsuch as various optical films or transparent protective glass islaminated on an LED module for self-luminous displays made by anencapsulant sheet for protecting light emitting elements being laminatedon the surface of a light emitting side of the light emitting module inwhich the light emitting elements such as LED elements are mounted to awiring substrate (refer to Patent Documents 2 and 3).

In the encapsulant sheet for forming the aforementioned LED module forself-luminous displays, for example, it has been demanded to be superiorin adhesiveness between the glass epoxy resin, the glass plate or thelike constituting the substrate of the aforementioned LED module and. Asan example of such an encapsulant sheet superior in adhesiveness, anencapsulant material made to contain polyethylene is disclosed in PatentDocument 2, and an encapsulant material made to contain an acid-modifiedpolyethylene which is more superior in glass adhesiveness is disclosedin Patent Document 3.

However, the LED module for self-luminous displays is produced by athermal lamination process which integrates a laminate body made by alight emitting module and encapsulant sheet being laminated, and thermalpress bonds this in a state placed on a heated plate. In this process,in order to secure sufficient releasability required after completion ofthe above-mentioned process between the encapsulant sheet havingsuperior adhesiveness and the above-mentioned heated plate, it has beennecessary to interpose various mold release films consisting ofpolyester resin or the like between the encapsulant sheet and the heatedplate, upon performing the above-mentioned thermal press bonding.

However, when performing the above-mentioned thermal lamination processby interposing a mold release film, not only does the consumption costof the mold release film accumulate, there have been cases where thesmoothness of the encapsulant sheet surface is impaired, due to fineunevenness in the surface of the mold release film, deformationaccompanying heating, etc. Loss in smoothness of the encapsulant sheetsurface is linked to a decline in the optical properties of theself-luminous display or long term durability. At the production site ofLED modules for self-luminous displays, the development of a technicalmeans which can avoid a quality decline and deterioration inproductivity accompanying the use of a mold release film has beendemanded.

The third embodiment has been made taking account of the above suchsituation, and has an object of providing an encapsulant sheet forself-luminous displays which enables to produce LED modules forself-luminous displays at higher productivity, while keeping quality atleast equal to conventional, even without using a mold release film.

The present inventors thoroughly researched, a result of which foundthat the above-mentioned problem could be solved by an encapsulant sheethaving asymmetrical adhesiveness on both sheet surfaces, for anencapsulant sheet for self-luminous displays, thereby arriving atcompleting the third embodiment. Hereinafter, the third embodiment willbe explained more specifically.

It should be noted that, due to being shared with the first embodiment,explanations of the self-luminous display, micro LED display device, LEDmodule and LED element will be omitted.

(Encapsulant Sheet)

The encapsulant sheet of the third embodiment is a resin sheet which canpreferably be used as a resin sheet laminated on the wiring substrate bycovering the light emitting elements in a “self-luminous display”, etc.on which a large number of micro light emitting elements, such as microLED television, and is a resin sheet superior in reworkability.

The encapsulant sheet of the third embodiment which can be preferablyused for a self-luminous display is a resin sheet which can bepreferably used as the resin sheet covering light emitting elements andlaminating on a wiring substrate, by having favorable molding propertyon one surface of an LED module on which a large number of micro lightemitting elements are mounted. Then, moreover, this encapsulant sheet isa resin sheet which makes the use of a release film upon thermallamination processing unnecessary, while maintaining at least equalquality of LED module, by having a suitable mold releasability on theother surface, thereby being able to contribute to an improvement inproductivity of LED modules and self-luminous display made using this.

The encapsulant sheet of the third embodiment, for example, is made as asheet-like member, by film forming an encapsulant composition with apolyethylene having a density of at least 0.870 g/cm³ and no more than0.930 g/cm³ as the base resin. Then, in the sheet-like state, it is aresin sheet with the main feature of the adhesive strength beingprepared in different ranges between one surface (adhesive surface) andthe other surface (peeling surface). It should be noted that the “baseresin” in the third embodiment shall refer to a resin, in a resincomposition containing this base resin, having the largest content ratioamong the resin component of this resin composition.

In this way, in an orthogonal direction relative to the sheet surface,so long as being a resin sheet having an asymmetrical structure asexplained in detail below regarding adhesiveness, this layerconfiguration is not limited to a specific configuration. Theencapsulant sheet may be a resin sheet of substantially single-layerstructure, in which adhesive component is unevenly distributed to theadhesive surface side, or a surface treatment to improve theadhesiveness or mold releasability is conducted on only one surface.Alternatively, it may be a two-layer configuration made by laminating anadhesive layer having adhesiveness to one side of the base layer havingmold releasability, or a three-layer configuration made by laminatingthe adhesive layer on one surface of the base layer and forming aspecial non-adhesive layer on the other surface, as in the encapsulantsheet (encapsulant sheet 1) shown in FIG. 4 .

Even in the case of the encapsulant sheet of the third embodiment beingany of the above-mentioned layer configurations, for the adhesivestrength of each surface of the encapsulant sheet, it is sufficient solong as the respective strengths measured by the “adhesion test”described in the next paragraph are respectively within predeterminedranges. More specifically, it is sufficient so long as the adhesivestrength of the adhesive surface is at least 5.0 N/15 mm and no morethan 50.0 N/15 mm, and is more preferably at least 5.0 N/15 mm and nomore than 12.0 N/15 mm. In addition, it is sufficient so long as theadhesive strength of the peeling surface is at least 0.1 N/15 mm and nomore than 3.0 N/15 mm, and is more preferably at least 0.3 N/15 mm andno more than 2.0 N/15 mm.

(Adhesion Test)

Adhesion Test: Adhesive strength of each surface is measured by adheringa surface on a side serving as a measurement target of an encapsulantsheet sample cut to a width of 15 mm onto a blue-sheet glass plate (75mm×50 mm×3 mm) and performing lamination processing in a vacuum heatedlaminator at 140° C. for 10 minutes, and performing a vertical peeling(50 mm/min) test with a peel tester (Tensilon universal testing machineRTF-1150-H) on the encapsulant sheet sample adhered on the blue-sheetglass plate.

In the encapsulant sheet 1 defined above, if the adhesive strength ofthe adhesive surface 124 is less than 5.0 N/15 mm, the initialadhesiveness in the manufacturing process of integration as an LEDModule tends to be insufficient. On the other hand, in the case of thisadhesive strength exceeding 50.0 N/15 mm, the elongation in tension ofthe encapsulant sheet, and thermal bonding tend to decline. In addition,by limiting the adhesive strength of the adhesive surface 124 at no morethan 12.0 N/15 mm, it is possible to secure the reworkability of theencapsulant sheet 1. Herein, “rework” in the third embodiment shallrefer to an operation of cutting part of the encapsulant sheet from theLED module without damaging normal LED elements, peeling off from thecircuit board, and replacing only part of the defective elements amongthe LED elements mounted to the circuit board. In addition,“reworkability” shall refer to the compliance of the above-mentionedoperation of “rework” of the encapsulant sheet, i.e. appropriate peelingease during this operation.

The encapsulant sheet of the third embodiment is preferably a resinsheet (encapsulant sheet 1) of three-layer configuration such as thatshown in FIG. 4 , as mentioned above. The encapsulant sheet 1 of FIG. 4is a resin sheet of three-layer configuration in which an adhesive layer122 is laminated on one surface of a base layer 111 with polyethylene asthe base resin, and a non-adhesive layer 121 is laminated on the othersurface thereof. In the encapsulant sheet 1 of this three-layerconfiguration, the surface of the non-adhesive layer 121 which is oneoutermost layer constitutes the peeling surface which is superior inmold releasability from heated plates (41, 42) of the laminator, and thesurface of the adhesive layer 122 which is the other outermost layerconstitutes the adhesive surface 124 superior in molding property andadhesiveness.

In the case of the encapsulant sheet 1 being a multi-layer resin sheetof three-layer configuration consisting of the base layer 111, theadhesive layer 122 and non-adhesive layer 121 laminated on both sidesthereof, the total thickness thereof is preferably at least 70 μm and nomore than 500 μm, and the thickness of the base layer 111 in this caseis preferably at least 50 μm and no more than 300 μm, and the thicknessof the adhesive layer 122 is preferably at least 10 μm and no more than100 μm in order to realize favorable molding property. The thickness ofthe non-adhesive layer 121 is sufficient so long as on the order of atleast 5 μm and no more than 30 μm; however, it is preferably set as athickness of the same order as the adhesive layer 122. This is because,when establishing the encapsulant sheet as a multi-layer resin sheet ofthe aforementioned such three-layer configuration, in the case offorming with resins having greatly different melting points anddensities in the adhesive layer 122 and non-adhesive layer 121 laminatedon both surfaces thereof, curl deformation tends to occur in themanufacturing process, and there is a risk of the ease in handling ofthe encapsulant sheet declining.

However, in the case of the LED element which is the target for coatingbeing a very small-sized LED element having a height no more than 10 μm,for the total thickness of the encapsulant sheet of the thirdembodiment, even in the case of being any layer configuration, the totalthickness is preferably at least 25 μm and no more than 100 μm, and inthe case of being a multi-layer sheet of three layers as in theencapsulant sheet 1 shown in FIG. 4 , the thickness of an adhesive layer122 within the above-mentioned total thickness layer is preferably atleast 5 μm and no more than 30 μm. In addition, the thickness of thenon-adhesive layer 121 is sufficient so long as on the order of at least5 μm and no more than 30 μm; however, it is preferably set as athickness of the same order as the adhesive layer 122 for the samereason as described above.

In the third embodiment, depending on the size of the LED element whichis the coating target, by the total thickness of the encapsulant sheetbeing at least 50 μm, or at least 5 μm, it is possible to sufficientlyprotect the LED element from external impact. On the other hand, if thethickness of the encapsulant sheet is no more than 1000 μm, it will tendto exhibit a molding property in the thermal lamination process. Morespecifically, during the hot pressing in a state coating the LEDelements, it tends to carry out favorable lamination without gaps by theresin constituting the encapsulant sheet sufficiently wrapping aroundthe surface irregularities of the surface of the wiring substrate onwhich LED elements are mounted. In addition, in the case of the LEDelements which are the target of coating being very small-sized LEDelements having a height no more than 10 μm, if the thickness of theencapsulant sheet is no more than 100 μm, the light transmittance of theencapsulating layer consisting of the encapsulant sheet tends to bemaintained at a favorable level in the self-luminous display afterintegration.

As the base resin of the resin composition forming the encapsulant sheetof the third embodiment, for example, it is possible to use polyolefin,and preferable to use a polyethylene having a density of at least 0.870g/cm³ and no more than 0.930 g/cm³. It should be noted that, in the caseof the encapsulant sheet being formed by a plurality of resin layers ofdifferent densities, it is sufficient if the density of the resin layerwhich has the lowest density is at least 0.870 g/cm³, and the density ofthe resin layer which has the highest density is no more than 0.930g/cm³.

In the encapsulant sheet 1 which is a multi-layer sheet of three-layerconfiguration, it is preferable to establish the base resin of the baselayer 111 as a resin more superior in heat resistance than the baseresin of the adhesive layer 122. More specifically, as the base resin ofthe base layer 111, it is preferable to use a polyethylene having adensity of at least 0.890 g/cm³ and no more than 0.925 g/cm³, and morepreferable to use a polyethylene having a density of at least 0.895g/cm³ and no more than 0.920 g/cm³. By setting the density of the baseresin of the base layer 111 as no more than 0.925 g/cm³, it is possibleto maintain the adhesiveness to the wiring substrate or the like of theencapsulant sheet in a preferred range. In addition, by setting thisdensity to at least 0.890 g/cm³, it is possible to impart the heatresistance required in the encapsulant sheet 1, without subjecting tocross-linking treatment.

In the encapsulant sheet 1 which is a multi-layer sheet of three-layerconfiguration, the base resin of the adhesive layer 122 preferably usesa polyethylene having a density of at least 0.870 g/cm³ and no more than0.920 g/cm³, and more preferable uses a polyethylene having a density ofat least 0.895 g/cm³ and no more than 0.915 g/cm³. In this case, bysetting the density of the base resin of the adhesive layer 122 as nomore than 0.920 g/cm³, it is possible to maintain the adhesiveness tothe wiring substrate or the like of the encapsulant sheet 1 in apreferred range. In addition, by setting this density to at least 0.870g/cm³, it is possible to impart the heat resistance required in theencapsulant sheet 1, without subjecting to cross-linking treatment.

In the encapsulant sheet 1 which is a multi-layer sheet of three-layerconfiguration, the base resin of the non-adhesive layer 121 preferablyuses a polyethylene having a density of at least 0.890 g/cm³ and no morethan 0.930 g/cm³, and more preferable uses a polyethylene having adensity of at least 0.900 g/cm³ and no more than 0.925 g/cm³. In thiscase, by setting the density of the base resin of the non-adhesive layer121 as no more than 0.930 g/cm³, it is possible to impart minimaladhesiveness in a range not inhibiting the mold releasability requiredin the encapsulant sheet 1. In addition, by setting this density to atleast 0.890 g/cm³, it is possible to maintain the mold releasability ofthe encapsulant sheet 1 at a preferable level.

As the base resin of the encapsulant composition for each layer formingthe encapsulant sheet of the third embodiment, in more detail, it ispossible to preferably use low-density polyethylene (LDPE), linearlow-density polyethylene (LLDPE) or metallocene linear low-densitypolyethylene (M-LLDPE). Thereamong, M-LLDPE which is synthesized usingmetallocene catalyst which is a single-site catalyst has few branches ofside chains, and uniform distribution of comonomer; therefore, by themolecular weight distribution being narrow, and being easy to makeultra-low density, it is possible to establish the adhesiveness of theencapsulant sheet relative to the wiring substrate 20 consisting ofglass epoxy resin plate, glass plate or the like in the LED module 30,and the self-luminous display such as the micro LED display device 100to be more superior.

Among the respective layers configuring the encapsulant sheet of thethird embodiment, the silane component in the adhesive layer 122 ispreferably contained within a specific content range. The content of the“silane component” in the resin component of the adhesive layer 122 ispreferably at least 0.02% by mass and no more than 0.19% by mass, andmore preferably at least 0.02% by mass and no more than 0.15% by mass.If the content of the silane component in the resin component of theadhesive layer is less than 0.02% by mass, the initial adhesiveness inthe manufacturing process of integrating as the LED module tends to beinsufficient. On the other hand, in the case of the content of thesilane component exceeding 0.19% by mass, relative to the increase insilane component, the adhesive strength hardly increases more than this,and the tendency strengthens for the burden of material cost becomingmore apparent. In addition, in this case, deterioration of the silanecomponent during storage tends to occur, and there is also a tendency ofthe tensile strength of the encapsulant sheet and the heat fusiondeclining. In addition, by limiting the content of silane component inthe resin component of the adhesive layer to no more than 0.15% by mass,it is possible to secure the reworkability of the encapsulant sheet.

On the other hand, among the respective layers configuring theencapsulant sheet of the third embodiment, it is preferable for silanecomponent not to be contained in the non-adhesive layer 121 in order tomaintain the mold releasability suited to the peeling surface. Inaddition, even if silane component is contained, the content thereof ispreferably less than 0.02% by mass in the resin component of thenon-adhesive layer 121.

In the encapsulant sheet 1 which is a multi-layer sheet of three-layerconfiguration, containing a silane component in the base layer 111 isoptional, and may be contained in a proportion no more than 0.06% bymass in the resin component of the base layer 111. However, for example,in the case of one surface of the base layer 111 being exposed at thetopmost surface of the encapsulant sheet 1 as the outermost layer, andforming the peeling surface by this surface, as in the case of theaforementioned resin sheet of two-layer configuration, it is preferablefor silane component not to be contained in the base layer 111, and evenif silane component is contained, the content thereof is preferably lessthan 0.02% by mass.

It should be noted that, in the encapsulant sheet of the thirdembodiment, the majority of this “silane component” contained in theadhesive sheet, i.e. at least 70% by mass and no more than 100% by massof silane component in this silane component, is a “graft silanecomponent” which is graft-polymerizing to the polyolefin that is thebase resin, and the proportion of “unreacted silane component” notgraft-polymerizing to the same base resin in this silane component ispreferably no more than 30% by mass. By the proportion of “graft silanecomponent” in the silane component being at least 70% by mass, i.e. theabove proportion of “unreacted silane component” being no more than 30%by mass, it is possible to lengthen the use expiration date (shelf life)of the encapsulant sheet for self-luminous displays. More specifically,in the case of the above proportion of this “unreacted silane component”exceeding 30% by mass, (shelf life) upon storing in an environment at23° C. and 50%, i.e. the period for which the adhesiveness retentionrate between the encapsulant sheet and glass epoxy substrate immediatelyafter film formation is at least 80%, is on the order of 3 to 6 months;whereas, by suppressing this proportion to less than 30% by mass, itbecomes possible to make this period (shelf life) 12 to 18 months.

It should be noted that “silane component”, “graft silane component” and“unreacted silane component” explanations in the third embodiment areshared with the explanations of “silane component in the secondembodiment, and thus are omitted.

(Production Method of Encapsulant Sheet)

The encapsulant sheet of the third embodiment can be produced bysubjecting the encapsulant composition for forming each layer for whichthe composition details were described above, to the film formation stepof melt forming into sheet form. This melt formation can be carried outby a formation method normally used for usual thermoplastic resins, i.e.various formation methods such as injection molding, extrusion molding,vacuum molding, compression molding and rotary molding. As the formationmethod of a multi-layer sheet, as one example, a molding method bycoextrusion by at least two types of melt kneading extruders, or amethod of joining by dry laminating after film forming separately eachlayer can be exemplified.

For example, the content of silane component in the polyolefin as thebase resin of the encapsulant composition for the adhesive layer isfound to preferably be within the range of at least 0.02% by mass and nomore than 0.19% by mass; however, it is possible to stably acquire theeffects of the third embodiment by performing trial film formation inadvance, performing final adjustment by determining the optimal valuefor the content of silane component in the encapsulant composition fromthe measurement results of the adhesive strength of each layer of thesample encapsulant sheet thereby obtained, and subsequently continuingproduction using encapsulant compositions of the same composition.

(Production Method of LED Module for Self-Luminous Displays)

The LED module 30 for self-luminous displays constituting the micro LEDdisplay device 100 can be obtained by subjecting to a thermal laminationprocess of making a laminate body by laminating the wiring substrate 20on which the LED elements 10 are mounted, and the encapsulant sheet 1,and integrating by thermal press bonding in a state placing thislaminate body on a heated plate.

As shown in FIG. 5 , this thermal lamination process can be performed byplacing the above-mentioned laminate body on the heated plate 41 of thelaminator 40 on the side of the encapsulant sheet 1 either directly orvia an auxiliary heated plate 42, and pressure bonding a laminate bodyholding plate 43 by vacuum drawing in this state to the laminate body.It should be noted that the auxiliary heated plate 42 is an auxiliarymember arranged for compensating for a deficiency in smoothness of thesurface of the heated plate 41 consisting of an iron plate or the like,and usually, a glass plate such as blue-sheet glass having thermalconductivity and surface smoothness is used. The “heated plate” of thethird embodiment is not limited to one configured from only the heatedplate 41. In the case of the auxiliary heated plate 42 being laminatedon the heated plate 41, the laminated body consisting of both isconsidered as the “heated plate”.

Conventionally, in the case of placing the laminate body configuring theLED module 30 for self-luminous displays on the heated plate 41 (42) ina state facing the encapsulant sheet, it has been necessary to interposea mold release film between the encapsulant sheet and heated plate 41(42) in order to allow release while maintaining the smoothness of theencapsulant sheet surface after heating. In contrast, by establishingthe encapsulant sheet as the encapsulant sheet 1 of the third embodimenthaving a different layer configuration than the conventional article, itis possible to place this laminate body directly on the heated plate 41(42) of the laminator 40 and integrate without going through a moldrelease film, during thermal press bonding of the above-mentionedlaminate body.

Placement of the above-mentioned laminate body on this heated plate 41(42) is carried out by directly placing the peeling surface 123 of theencapsulant sheet on the heated plate 41 (42) without going through amold release film. So long as being the encapsulant sheet 1 ofthree-layer configuration consisting of the adhesive layer 122, baselayer 111 and non-adhesive layer 121, it will create a laminate bodyconfiguring the LED module 30 for self-luminous displays so that thesurface of the non-adhesive layer 121 serving as the peeling surface 123of the encapsulant sheet 1 is exposed at the topmost surface. Then, asshown in FIG. 6 , thermal pressure bonding is performed in a statedirectly placing the surface of this non-adhesive layer 121 on theheated plate 41 (42). It should be noted that, at this time, in theadhesive surface 124 consisting of the adhesive layer 122 of theencapsulant sheet 1, the resin forming the encapsulant sheet exhibitssufficient molding property, and adheres with favorable adhesivestrength to the wiring substrate 20 on which the LED elements 10 aremounted.

It should be noted that, normally, with a conventional, general moldrelease film, since the adhesive material is assumed as the adherend,the smoothness of the surface of this film is often deficient in thesmoothness demanded in the surface of the encapsulant sheet forself-luminous displays. By using the encapsulant sheet of the thirdembodiment, since it is possible to perform the thermal laminationprocess by excluding a conventional, general mold release film, forexample, by using the auxiliary heated plate 42 made of glass which issuperior in surface smoothness as the auxiliary heated plate 42, it ispossible to avoid this problem, and stably keep the surface smoothnessof the encapsulant sheet at a high level.

It should be noted that the above-mentioned thermal lamination processis preferably sequentially performed by dividing into the two stagesprocessing of an initial lamination processing and final curingprocessing. This is because, by performing the thermal laminationprocess by dividing into the initial lamination processing of causingthe encapsulant sheet to follow the uneven surface of the wiringsubstrate on which the LED elements are mounted without producingbubbles, and adhering, and the final curing processing of furtherincreasing the adhesion after adhering to make an article with stableadhesion, it becomes possible to produce the LED module 30 forself-luminous displays under higher quality and stability.

(Production Method of Self-Luminous Display)

By further laminating and integrating the display panel 2 by adhering,sticking or the like to the LED module 30 which can be obtained by theabove-mentioned production method, it is possible to produce the microLED display device 100 shown in FIG. 2 , or various self-luminousdisplays consisting of a similar layer configuration.

Herein, for example, in the micro LED display device 100, a blacklight-shielding layer is normally arranged as an optical memberconfiguring the display panel 2. This black light-shielding layer can beconfigured by establishing a sticking layer which bonds the encapsulantsheet 1 and display panel as a black layer, for example. By using theencapsulant sheet 1 of the third embodiment as the encapsulant sheet,the encapsulant sheet 1 can contribute to an improvement in overallproductivity of self-luminous displays such as the micro LED displaydevice 100, also in the point of reworking (re-sticking) of thissticking layer portion becoming possible

Fourth Embodiment Encompassed by Present Embodiment

The fourth embodiment specifically provides the following.

A thirty-second aspect of the present invention is a direct backlightcomprising: the encapsulant sheet as described in any one of the firstto tenth aspects; and a light emitting module in which a plurality oflight emitting elements is mounted to a wiring substrate, in which theencapsulant sheet is laminated to the light emitting module to cover thelight emitting element and the wiring substrate.

According to the thirty-second aspect of the present invention, it ispossible to acquire the above respective effects which can be exhibitedby the encapsulant sheet as described in any one of the first to tenthaspects, and obtain a direct backlight superior in opticalcharacteristics, durability and productivity.

According to a thirty-third aspect of the present invention, in thedirect backlight as described in the thirty-second aspect, the lightemitting element is an LED element.

According to a thirty-fourth aspect of the present invention, in thedirect backlight as described in the thirty-third aspect, the LEDelement has an LED light emitting chip and a resin cover which coversthe LED light emitting chip, width and depth of the LED element are bothno more than 300 μm, and height is no more than 200 μm, and anarrangement interval of each of the LED elements is at least 0.03 mm andno more than 100 mm.

According to a thirty-fifth aspect of the present invention, in thedirect backlight as described in the thirty-fourth aspect, width anddepth of the LED element are both no more than 50 μm, and height is nomore than 10 μm, and an arrangement interval of each of the LED elementsis at least 0.05 mm and no more than 5 mm.

Any of the thirty-third to thirty-fifth aspects of the present inventioncan obtain direct backlight-type LED display devices superior in opticalcharacteristics, durability and productivity, while dealing with thesize and arrangement of various LED elements.

According to a thirty-sixth aspect of the present invention, the directbacklight as described in any one of the thirty-second to thirty-fifthaspects, comprises a light emitting surface made by a plurality of thelight emitting modules being joined on the same plane, in which theencapsulant sheet is laminated on the light emitting surface.

The thirty-sixth aspect of the present invention carries out enlargementof the screen size of various LED display devices, by joining aplurality of direct backlights configured using the above-mentionedencapsulant sheet according to the present invention. Theabove-mentioned encapsulant sheet according to the present invention issuperior in surface smoothness after joining by thermal lamination;therefore, it is possible to perform screen enlargement of the LEDdisplay device with a high degree of design freedom, without causing adecline in screen quality accompanying the joining of theabove-mentioned direct backlight modules.

A thirty-seventh aspect of the present invention is an LED displaydevice comprising: the direct backlight as described in any one of thethirty-second to thirty-sixth aspects; a diffusion panel; and a displaypanel, in which the diffusion plate is laminated to the peeling surfaceof the encapsulant sheet configuring the direct backlight.

According to the thirty-seventh aspect of the present invention, it ispossible to establish a device superior in productivity and durabilityof a direct backlight-type LED display device.

A thirty-eighth aspect of the present invention is a direct backlightcomprising: the encapsulant sheet as described in any one of thesixteenth to nineteenth aspects; and a light emitting module in which aplurality of light emitting elements is mounted to a wiring substrate,in which the encapsulant sheet is laminated to the light emitting moduleto cover the light emitting elements and the wiring substrate.

According to the thirty-eighth aspect of the present invention, it ispossible to acquire the above respective effects which can be exhibitedby the encapsulant sheet as described in any one of the sixteenth tonineteenth aspects, and obtain a direct backlight superior in opticalcharacteristics, durability and productivity.

A thirty-ninth aspect of the present invention is an LED display devicecomprising: the direct backlight as described in the thirty-eighthaspect; a diffusion panel; and a display panel, in which the diffusionplate is laminated to the peeling surface of the encapsulant sheetconfiguring the direct backlight.

According to the thirty-ninth aspect of the present invention, it ispossible to acquire the above respective effects which can be exhibitedby the direct back light of the thirty-eighth aspect, and obtain an LEDdisplay device superior in optical characteristics, durability andproductivity.

A fortieth aspect of the present invention is a reworking method of thedirect backlight as described in the thirty-eighth aspect, comprising:sequentially performing a thermal lamination step divided into twostages of processing of an initial lamination processing and finalcuring processing to integrate a laminate body including a lightemitting module and an encapsulant sheet laminated to cover lightemitting elements configuring the light emitting module; and performinga reworking step accompanying an operation to cut out a part of theencapsulant sheet and peel from the light emitting module, aftercompletion of the initial lamination processing and before start of thefinal curing processing.

The fortieth aspect of the present invention can achieve at preferablelevels both adhesion durability during long term use as an LED displaydevice, and reworkability in the manufacturing stage process, for adirect backlight configured using the encapsulant sheet as described inthe sixteenth aspect, for example.

A forty-first aspect of the present invention is a backlight comprising:the encapsulant sheet as described in any one of the twenty-fifth totwenty-eighth aspects; and a light emitting module in which a pluralityof light emitting elements is mounted to a wiring substrate, in whichthe encapsulant sheet is laminated to the light emitting module to coverthe light emitting element and the wiring substrate. According to theforty-first aspect of the present invention, it is possible to acquirethe above respective effects which can be exhibited by the encapsulantsheet as described in any one of the twenty-fifth to twenty-eighthaspects, and obtain a direct backlight superior in opticalcharacteristics, durability and productivity.

A forty-second aspect of the present invention is a liquid crystaldisplay comprising: the direct backlight as described in the forty-firstaspect; a diffusion panel; and a display panel, in which the diffusionplate is laminated to the peeling surface of the encapsulant sheetconfiguring the direct backlight.

According to the forty-second aspect of the present invention, it ispossible to acquire the above respective effects which can be exhibitedby the direct backlight of the forty-first aspect, and obtain a liquidcrystal display superior in optical characteristics, durability andproductivity.

A forty-third aspect of the present invention is a production method ofthe direct backlight as described in the forty-first aspect, comprising:a thermal lamination step of integrating a laminate body in which thelight emitting module and the encapsulant sheet are laminated, bythermal press bonding in a state placing on a heated plate includingmetal and/or glass, in which the thermal press bonding is performed bydirectly placing the peeling surface of the encapsulant sheetconfiguring the laminate body on the heated plate, without going througha mold release film.

The forty-third aspect of the present invention defines the technicalconcept according to the twenty-fifth aspect of the present invention asa production method of direct backlights. This production method canproduce the direct backlight with higher productivity, while keepingquality which is at least equal to conventional, even without using amold release film, by using the encapsulant sheet combining adhesivenessto the circuit board surface having fine unevenness, and moldreleasability from a heated plate on which placed during thermallamination processing.

Hereinafter, the fourth embodiment will be explained more specifically.It should be noted that, due to sharing with the first, second or thirdembodiment, an explanation for the encapsulant sheet will be omitted.

(Direct Backlight)

The liquid crystal display includes a display screen such as a liquidcrystal display panel, and a backlight which illuminates this displayscreen from the back side. For example, in the liquid crystal displayconsisting of the basic configuration shown in FIG. 7 , a directbacklight system can be adopted.

The direct backlight which is the fourth embodiment of the presentinvention, for example, is a light source unit which can be used as thelight source of a liquid crystal display of the aforementioned directbacklight system, and as the encapsulant sheet for encapsulating thelight emitting device such as LED elements used in the light source, itis configured to use the encapsulant sheet of the first to thirdembodiments according to the present invention explained above.

As one preferred example of the direct backlight which is the fourthembodiment, it is possible to exemplify a direct LED backlight 200having the layer configuration shown in FIG. 8 . The direct LEDbacklight 200 is a light emitting module in which a plurality of the LEDelements 10 is mounted to the wiring substrate 20, and is aconfiguration in which the encapsulant sheet 1 of the first to thirdembodiments according to the present invention is laminated in a formcoating the LED elements 10 and writing board 20. As shown in FIG. 8 ,in the direct LED backlight 200, the optical member such as thediffusion plate 5 is laminated on the LED elements 10 via theencapsulant sheet 1.

As shown in FIG. 8 , in the wiring substrate 20 constituting the directLED backlight 200, a wiring part 22 is normally formed on the supportsubstrate 21 via an adhesive agent layer 24. An insulative protectivefilm 25 is formed on the support substrate 21 and wiring part 22, andfurther, a reflective layer 26 consisting of a white resin or the likeis laminated on the insulative protective film 25. In addition, the LEDelements 10 consisting of an LED light emitting chip 11 and lightdiffusion lens 13 are mounted on the wiring part 22 in an electricallyconductible state, via a solder layer 23.

Upon securing the required molding property, by using the encapsulantsheet according to the present invention for which excessive flow ofmaterial resin during a heating process is suppressed, it is possible toimprove the optical characteristic, durability and productivity of thedirect backlight and the liquid crystal display made using this,similarly to the above-mentioned self-luminous display.

Other Embodiments Encompassed by Present Embodiment

The present invention is not limited to the above explained first tofourth embodiments. For example, it is possible to preferably configurea small-scale LED display device, or light source unit of variousillumination devices other than a display device, similarly to asdescribed above.

EXAMPLES

Hereinafter, although the present embodiment is explained morespecifically by way of the Examples, the present embodiment is not to belimited to the following examples.

1. First Examples

(Production of Encapsulant Sheet)

Using a film molding machine having a 30-mm diameter extruder and T dieof 200-mm width, the below encapsulant composition formulated for everyExample and Comparative Example was made into sheet form with anextruding temperature of 210° C., take-over speed of 1.1 m/min and filmthickness of 400 μm to produce the encapsulant sheets of each Exampleand Comparative Example. It should be noted that for the cooling rollerimmediately below the T die and the rubber roller, the cooling rolleremploys a chrome-plated polished cooling roller with surface roughnessRz of 1.5 μm, and the rubber roller employed a silicone rubber roller of70 degree hardness. The densities of the encapsulant sheets of eachExample and Comparative Example after film production were as listed inTable 1.

Encapsulant Sheet of Example 1-1 (1-1-1˜1-1-2)

Relative to 100 parts by mass of the following base resin 1, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 20 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 1-1 (1-1-1˜1-1-2).

-   -   Base Resin 1: Metallocene linear low-density polyethylene        (M-LLDPE) with density of 0.901 g/cm³, melting point of 93° C.,        and MFR at 190° C. of 2.0 g/10 min.    -   Additive Resin 1 (weatherproofing agent master batch): Relative        to 100 parts by mass of low-density polyethylene with 0.919        g/cm³ density and MFR at 190° C. of 3.5 g/10 min, KEMIS    -   TAB62(HALS): 0.6 parts by mass    -   KEMISORB12 (UV absorber): 3.5 parts by mass    -   KEMISORB79 (UV absorber): 0.6 parts by mass    -   Additive Resin 2 (silane-modified polyethylene): Silane-modified        polyethylene obtained by mixing 2 parts by mass of vinyl        trimethoxysilane and 0.15 parts by mass of dicumylperoxide as a        radical generator (reaction catalyst) relative to 100 parts by        mass of metallocene linear low-density polyethylene having        density of 0.900 g/cm³ and MFR of 2.0 g/10 min, then melting at        200° C. and kneading. The density of this additive resin 2 is        0.901 g/cm³, and MFR is 1.0 g/10 min.

Encapsulant Sheet of Example 1-2 (1-2-1˜1-2-2)

Relative to 100 parts by mass of the following base resin 2, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 20 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 1-2 (1-2-1-1-2-2).

-   -   Base Resin 2: Metallocene linear low-density polyethylene        (M-LLDPE) having density of 0.898 g/cm³ and MFR at 190° C. of        3.5 g/10 min.

Encapsulant Sheet of Example 1-3 (1-3-1˜1-3-2))

Relative to 100 parts by mass of the following base resin 3, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 20 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 1-3 (1-3-1˜1-3-2).

-   -   Base Resin 3: Metallocene linear low-density polyethylene        (M-LLDPE) having density of 0.905 g/cm³ and MFR at 190° C. of        3.5 g/10 min.

Encapsulant Sheet of Example 1-4 (1-4-1˜1-4-2))

Relative to 100 parts by mass of the following base resin 4, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 20 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 1-4 (1-4-1-1-4-2).

-   -   Base Resin 4: metallocene linear low-density polyethylene        (M-LLDPE) having density of 0.919 g/cm³ and MFR at 190° C. of        3.5 g/10 min.

Encapsulant Sheet of Comparative Example 1-1

Relative to 100 parts by mass of the following base resin 5, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 3 parts by mass and 10 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Comparative Example 1-1.

-   -   Base Resin 5: Metallocene linear low-density polyethylene        (M-LLDPE) having density of 0.870 g/cm³ and MFR at 190° C. of        1.0 g/10 min.

Encapsulant Sheet of Comparative Example 1-2

Relative to 100 parts by mass of the following base resin 6, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 20 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Comparative Example 1-2.

-   -   Base Resin 6: Metallocene linear low-density polyethylene        (M-LLDPE) having density of 0.880 g/cm³ and MFR at 190° C. of        30.0 g/10 min.        <Evaluation of Encapsulant Sheet>        (Melt Viscosity of Encapsulant Sheet)

The “melt viscosity (η) at shear velocity 2.43×10 sec⁻¹” of eachencapsulant sheet of the Examples and Comparative Examples was measuredbased on JIS K7199 using a Capillograph 1-B manufactured by Toyo SeikiSeisaku-sho, Ltd. and using a capillary tube with setting temperature of120° C. and D=1 mm, L/D=10. The results are shown as “melt viscosity” inTable 1.

(Vicat Softening Point of Encapsulant Sheet)

The Vicat softening point of each encapsulant sheet of the Examples andComparative Examples was measured based on ASTM D1525. The results areshown as “Vicat softening point” in Table 1.

(MFR of Encapsulant Sheet)

The MFR of each encapsulant sheet of the Examples and ComparativeExamples was measured based on JIS K7210 at conditions of 190° C. and2.16 kg load. The results are shown as “MFR” in Table 1.

(Durometer A Hardness Measurement of Encapsulant Sheet)

For each encapsulant sheet of the Examples and Comparative Examples,test pieces for hardness measurement with 3 mm thickness were preparedby laminating a plurality of encapsulant material sheets and performingvacuum laminating, and the Durometer A hardness was measured based onJIS K7215. The results are shown as “Hardness” in Table 1.

Evaluation Example 1: Molding Property

For each encapsulant sheet of the Examples and Comparative Examples, themolding property relative to various uneven surfaces was measured by thefollowing test method.

Module Creation for Molding Property Test

-   -   Sample 1 (noted as “micro” in list of module irregular surface        in Table 1):A total of 15,251 pseudo LED elements made by        molding a thermosetting-type epoxy resin so as to have the same        external form as an LED element of the micro size of 25 μm        width×15 μm depth×2.5 inn height were formed at a pitch of 2 mm        on the surface of a glass epoxy substrate of 200×300-mm size,        any encapsulant sheet of the respective Examples and Comparative        Examples of 300 μm thickness was laminated on the pseudo LED        element arrangement surface of this glass epoxy substrate, and a        50-μm ethylene tetrafluoroethylene (ETFE) film which has been        single-side corona treated was further laminated on this        encapsulant sheet as a surface protective film, vacuum        lamination processing was performed at conditions of 150° C., 5        minutes vacuum drawing, 10 minutes press holding at 70 KPa upper        chamber pressure, using a vacuum laminator for solar cell module        manufacturing, thereby creating a module for molding property        testing (Sample 1).    -   Sample 2 (noted as “small” in list of module uneven surface in        Table 1):Other than setting the size of pseudo LED element as        100 μm width×200 μm depth×100 μm height, setting the arrangement        pitch thereof as 10 mm, and forming a total of 336, the module        for molding property test (Sample 2) was prepared with the same        material and method as Sample 1.    -   Molding property test: Each of the above-mentioned modules for        testing was visually observed, and the molding characteristic        was evaluated according to the following evaluation criteria.        Evaluation Criteria    -   A: Perfectly follows unevenness of LED element arrangement        surface opposed by encapsulant sheet    -   Formation of voids was not observed.    -   B: No more than three bubbles of no more than 2 mm² observed.    -   C: Does not perfectly follow unevenness of LED element        arrangement surface opposed by part of encapsulant sheet, and        partially laminated defective portion (void) formed in vicinity        of pseudo LED element.        Evaluation results noted in Table 1 as “Molding property”.

Evaluation Example 2: Film Thickness Uniformity

For each encapsulant sheet of the Examples and Comparative Examples, thefilm thickness uniformity was measured and evaluated by the followingtest method using each of the above-mentioned modules for testing, forfilm thickness uniformity after vacuum laminating performed in theabove-mentioned molding test. Film thickness uniformity test: A laminatebody was made of a configuration made by laminating 50-μm untreated ETFEon the back surface of each encapsulant sheet of the Examples andComparative Examples cut to 30×30 cm as a mold releasing film, andsubsequently, further laminating 30×30 cm glass of 3-mm thickness on theback surface, and vacuum lamination processing was performed on thislaminate body at the same conditions as Evaluation Example 1. Aftercooling, the glass and ETFE were peeled, and for the thickness of theencapsulant sheet, the film thickness of at least two points of thecentral portion and a location 2 cm from the corner towards the centerwere measured with a digital thickness gauge, and the film thicknessuniformity was evaluated according to the following evaluation criteria.

Evaluation Criteria

-   -   A: Film thickness difference between central part and location 2        cm from corner less than 12 μm (3%)    -   B: Film thickness difference between central part and location 2        cm from corner at least 12 μm (3%) and less than 32 μm (8%). C:        Film thickness difference between central part and location 2 cm        from corner at least 32 μm (8%). The evaluation results are        noted in Table 1 as “Film thickness uniformity”.

TABLE 1 Encapsulant sheet Vicat Melt softening Film Density viscositypoint MFR Module Molding thickness (g/cm³) (poise) (° C.) (g/10 min.)Hardness unevenness property uniformity Example 1-1 0.902 8.7 × 10⁴ 801.9 91 Micro A A Example1-2 Small B — Example2-1 0.900 7.6 × 10³ 73 3.190 Micro A A Example2-2 Small B — Example3-1 0.905 7.6 × 10³ 84 3.1 93Micro A B Example3-2 Small B — Example4-1 0.916 7.7 × 10³ 85 3.1 93Micro A B Example4-2 Small B — Comparative 0.870 1.2 × 10⁵ 48 1.5 66Micro C A Example1 Comparative 0.905 1.6 × 10³ 84 12.3 73 Micro A CExample2

The encapsulant sheet of Comparative Example 1-1 came to haveinsufficient molding property irrespective of MFR being within a rangeconsidered desirable. On the other hand, the encapsulant sheet ofComparative Example 1-2 came to have insufficient uniformity in filmthickness for self-luminous display, irrespective of the density andVicat softening point being within ranges considered desirable. Inaccordance with these results, according to Table 1, the encapsulantsheet of the first example was found to have sufficient molding propertyto a fine uneven surface, and superior in film thickness uniformity, andthus suited to various self-luminous display applications such as microLED televisions.

2. Second Examples

(Production of Encapsulant Sheet)

Using a film molding machine having a 30-mm diameter extruder and T dieof 200-mm width, the below encapsulant composition formulated for everyExample and Comparative Example was made into sheet form with anextruding temperature of 210° C., take-over speed of 1.1 m/min and filmthickness of 400 μm to produce the encapsulant sheets of each Exampleand Comparative Example. It should be noted that for the cooling rollerimmediately below the T die and the rubber roller, the cooling rolleremploys a chrome-plated polished cooling roller with surface roughnessRz of 1.5 μm, and the rubber roller employed a silicone rubber roller of70 degree hardness. The densities of the encapsulant sheets of eachExample and Comparative Example after film production were as listed inTable 2.

Encapsulant Sheet of Example 2-1

Relative to 85 parts by mass of the following base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the following additive resin 2 (silane-modified polyethylene) weremixed in the proportion of 5 parts by mass and 10 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 2-1. The silane component amount in theresin component of this encapsulant sheet is 0.037% by mass.

-   -   Base Resin: Metallocene linear low-density polyethylene        (M-LLDPE) with density of 0.901 g/cm³, melting point of 93° C.,        and MFR at 190° C. of 2.0 g/10 min.    -   Additive Resin 1 (weatherproofing agent master batch): Relative        to 100 parts by mass of low-density polyethylene with density of        0.919 g/cm³ and MFR at 190° C. of 3.5 g/10 min, KEMIS    -   TAB62(HALS): 0.6 parts by mass.    -   KEMISORB12 (UV absorber): 3.5 parts by mass    -   KEMISORB79 (UV absorber): 0.6 parts by mass    -   Additive Resin 2 (silane-modified polyethylene): Silane-modified        polyethylene obtained by mixing 5 parts by mass of vinyl        trimethoxysilane and 0.15 parts by mass of dicumylperoxide as a        radical generator (reaction catalyst) relative to 95 parts by        mass of metallocene linear low-density polyethylene having a        density of 0.898 g/cm³ and MFR of 3.5 g/10 min, then melting at        200° C. and kneading. The density of this additive resin 2 is        0.901 g/cm³, and MFR is 1.0 g/10 min. In addition, as a result        of measuring the content (% by mass) of “graft silane component”        in this silane-modified polyethylene by the aforementioned ICP        emission spectral analysis, the graft silane component amount in        the additive resin 2 (silane-modified polyethylene) was 0.37% by        mass and the unreacted silane component was 0.05% by mass, and        88.1% by mass in all of these silane components was graft silane        component.

Encapsulant Sheet of Example 2-2

Relative to 87.5 parts by mass of the above-mentioned base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 7.5 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 2-2. The silane component amount in theresin component of this encapsulant sheet is 0.025% by mass.

Encapsulant Sheet of Example 2-3

Relative to 82.5 parts by mass of the above-mentioned base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 12.5 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 2-3. The silane component amount in theresin component of this encapsulant sheet is 0.047% by mass.

Encapsulant Sheet of Example 2-4

Relative to 80 parts by mass of the above-mentioned base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 15 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 2-4. The silane component amount in theresin component of this encapsulant sheet is 0.056% by mass.

Encapsulant Sheet of Example 2-5

Relative to 70 parts by mass of the above-mentioned base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 25 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Example 2-5. The silane component amount in theresin component of this encapsulant sheet is 0.093% by mass.

Encapsulant Sheet of Example 2-6

For the encapsulant compositions described below, using a film moldingmachine having a T die of 300-mm width and the first layer (adhesivelayer): 30-mm diameter extruder, second layer (base layer): 30-mmdiameter extruder and third layer (adhesive layer): 30-mm diameterextruder, the molten resins of the three layers of adhesive layer-baselayer-adhesive layer were made into sheet form in the configuration oflayer ratios 1:3:1, at an extruding temperature of 210° C., take-overspeed of 1.1 m/min and film thickness of 150 μm to produce theencapsulant sheet of Example 2-6. It should be noted that for thecooling roller immediately below the T die and the rubber roller, thecooling roller employs a chrome-plated polished cooling roller withsurface roughness Rz of 1.5 μm, and the rubber roller employed asilicone rubber roller of 70 degree hardness.

-   -   Encapsulant Composition for Adhesive Layer (First Layer and        Third Layer): A composition consisting of the same materials and        composition as the encapsulant sheet of the above Example 2-1        was used.    -   Encapsulant Composition for Base Layer (Second Layer): A        composition made by mixing the above-mentioned “additive resin 1        (weatherproofing agent master batch)” and “additive resin 2        (silane-modified polyethylene)” in the proportions of 5 parts by        mass and 1 parts by mass, respectively, relative to 94 parts by        mass of the above “Base Resin 1” was used. The silane component        amount in the resin component of the “adhesive layer” of this        encapsulant sheet is 0.037% by mass, similarly to the        encapsulant sheet of Example 2-1 (for Example 2-6, the silane        component amount listed in Table 2 is the content in this        adhesive layer).

Encapsulant Sheet of Comparative Example 2-1

Relative to 90 parts by mass of the following base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 5 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Comparative Example 2-1. The silane componentamount in the resin component of this encapsulant sheet is 0.019% bymass.

Encapsulant Sheet of Comparative Example 2-2

Relative to 45 parts by mass of the following base resin, theabove-mentioned additive resin 1 (weatherproofing agent master batch)and the above-mentioned additive resin 2 (silane-modified polyethylene)were mixed in the proportion of 5 parts by mass and 50 parts by mass,respectively, to make the encapsulant composition for molding theencapsulant sheet of the Comparative Example 2-2. The silane componentamount in the resin component of this encapsulant sheet is 0.190% bymass.

<Evaluation of Encapsulant Sheet>

(Gel Fraction of Encapsulant Sheet)

Regarding each encapsulant sheet of the Examples and ComparativeExamples, 0.1 g of each encapsulant sheet was placed on resin mesh, andextracted for 4 hours with toluene at 60° C., then after taking outevery resin mesh, drying and weighing, mass comparison of before andafter extraction was performed to measure the mass % of residualinsoluble matter, thereby measuring the gel fraction. The gel fractionfor all encapsulant materials was 0%.

First Adhesive Strength and Second Adhesive Strength of EncapsulantSheet

For each encapsulant sheet of the Examples and Comparative Examples, thefollowing first adhesion test and second adhesion test was performed,and the first adhesive strength and second adhesive strength for eachencapsulant sheet were measured. The results were as noted in Table 2.

First adhesion test: Lamination processing was performed in a vacuumheated laminator at 140° C. for 10 minutes by adhering the encapsulantsheet sample cut to the size of 75×50 mm on a glass epoxy plate (75mm×50 mm×0.05 mm), and in a state penetrating to immediately above theglass epoxy plate surface with 15 mm width in the encapsulant sheetsample adhered on the glass epoxy plate, making a cut serving as thestart for the peeling start location, and then performing a verticalpeeling (50 mm/min) test with a peel testing machine (Tensilon universaltesting machine RTF-1150-H) to measure a first adhesive strength. Secondadhesion test: Lamination processing was performed in a vacuum heatedlaminator at 140° C. for 10 minutes by adhering the encapsulant sheetsample cut to the size of 75×50 mm on a glass epoxy plate (75 mm×50mm×0.05 mm), and subsequently, curing treatment was further performed inthe vacuum heated laminator at 150° C. for 15 minutes, and in a statepenetrating to immediately above the glass epoxy plate surface with 15mm width in the encapsulant sheet sample adhered on the glass epoxyplate, making a cut serving as the start for the peeling start location,and then performing a vertical peeling (50 mm/min) test with a peeltesting machine (Tensilon universal testing machine RTF-1150-H) tomeasure a second adhesive strength.

(Adhesive Strength Durability Test)

For each of the Examples and Comparative Examples, after performingtwo-stage heat treatment processing (lamination processing and curingprocessing) by the same conditions as the above-mentioned secondadhesion test, durability test was further performed for 500 hours atthe condition of 85° C. and 85% with a moisture heat testing machine ofa convection circulation type, and after the elapse of 500 hours,measurement of the adhesive strength was performed by a peel testingmachine at the same conditions as the above-mentioned first and secondadhesion tests. The results were as noted in Table 2 as “500 h adhesivestrength”.

Evaluation Example 1: Reworkability

For each encapsulant sheet of the Examples and Comparative Examples,reworkability evaluation was carried out by the following test method. Apseudo LED element made by molding a thermosetting-type epoxy resin soas to have the same external form as an LED element of the size of 100μm width×100 μm depth×100 μm height was formed at a pitch of 2 mm on thesurface of a glass epoxy substrate of 200×300-mm size, any encapsulantsheet of the respective Examples and Comparative Examples of 150 μmthickness was laminated on the above-mentioned pseudo LED elementarrangement surface of this glass epoxy substrate, and a 50-μm ethylenetetrafluoroethylene (ETFE) film which has been single-side coronatreated was further laminated on this encapsulant sheet as a surfaceprotective film, vacuum lamination processing was performed atconditions of 140° C., 3 minutes vacuum drawing, 7 minutes press holdingat 70 KPa upper chamber pressure, using a vacuum laminator for solarcell module manufacturing, thereby conducting initial laminationprocessing. Subsequently, a part of the encapsulant sheet, which is aportion of an area of 2×2 mm size including one pseudo LED element wasassumed as a reworking portion and was peeled off with a scalpel with asharp tip, the existence/absence of cohesive peeling of the encapsulantsheet at the peripheral part of this peeling area (reworking portion)was confirmed, subsequently, an encapsulant piece obtained by cuttingthe same encapsulant sheet in a state prior to vacuum lamination to thesize of 2×2 mm was placed in the peeled off location, laminationprocessing (final curing processing) at the conditions of a temperatureof 150° C. and for 15 minutes was conducted again with the same methodas described above, and the external appearance of the above reworkedportion thereafter was observed to evaluate the reworkability. It shouldbe noted that, since the initial adhesion (first adhesive strength) forComparative Example 2-1 was insufficient, this evaluation was notcarried out.

Evaluation Criteria

-   -   A: No cohesive peeling of encapsulant sheet at edge part of        peeling range of encapsulant sheet, no damage of pseudo LED        element, and after final curing processing, the encapsulant        sheet perfectly followed unevenness of the LED element        arrangement surface including reworking portions, and the        external appearance was favorable.    -   B: Cohesive peeling of encapsulant sheet at edge part of peeling        range of encapsulant sheet was observed; however, no damage of        pseudo LED element, and after final curing processing, the        encapsulant sheet perfectly followed unevenness of the LED        element arrangement surface including working portions. However,        small foreign substances derived from the above cohesive peeling        remained in encapsulant sheet, and external appearance        deteriorated.    -   C: Cohesive peeling of encapsulant sheet at edge part of peeling        range of encapsulant sheet was observed, and pseudo LED element        was damaged while peeling off reworked portion.

Evaluation Example 2: Long Term Durability

Based on the above results of the adhesive strength durability test, thelong term durability of each encapsulant sheet of the Examples andComparative Examples was evaluated. Evaluation Criteria

-   -   A: “500 h adhesive strength” at least 10 N/15 mm    -   B: “500 h adhesive strength” at least 6 N/15 mm and less than 10        N/15 mm    -   C: “500 h adhesive strength” less than 6 N/15 mm        The evaluation results are noted in Table 2 as “Long term        durability”.

TABLE 2 First Second 500h Silane adhesive adhesive adhesive componentstrength strength strength Long term (mass %) (N/15 mm) (N/15 mm) (N/15mm) Reworkability durability Example1 0.037 5.8 11.6 10.5 A A Example20.025 4.1 9.7 9.5 A B Example3 0.047 6.0 14.0 12.1 A A Example4 0.0566.3 14.0 12.6 A A Example5 0.093 6.6 11.4 13.0 A A Example6 0.037 6.07.2 11.0 A A Comparative 0.019 1.6 7.2 5.2 — C Example1 Comparative 0.1912.0 16.0 15.8 C A Example2

According to Table 2, the encapsulant sheet for self-luminous displaysof the second example was found to be an encapsulant sheet combiningadhesion durability during long term use as a self-luminous display suchas a micro LED television, and reworkability in the manufacturing stage.

3. Third Examples

(Production of Encapsulant Sheet)

In order to create a multi-layer encapsulant sheet, encapsulantcompositions formulated for every layer of the first layer, second layerand third layer were made into sheet form using a film molding machine(30-mm diameter extruder) having a T die of 300-mm width, by coextrudingto make the layer order of first layer-second layer-third layer with anextruding temperature of 210° C., and take-over speed of 1.1 m/min,thereby producing the encapsulant sheets of each Example and ComparativeExample. It should be noted that for the cooling roller immediatelybelow the T die and the rubber roller, the cooling roller employs achrome-plated polished cooling roller with surface roughness Rz of 1.5μm, and the rubber roller employed a silicone rubber roller of 70degrees hardness.

Encapsulant Sheet of Example 3-1

Encapsulant Composition of First Layer (Adhesive Layer): The following“additive resin 1 (weatherproofing agent master batch)” and “additiveresin 2 (silane-modified polyethylene)” were mixed in the proportions of5 parts by mass and 15 parts by mass, respectively, relative to 80 partsby mass of the following “base resin 1”. The density of the first layer(adhesive layer) of the encapsulant sheet of Example 3-1 consisting ofthe above formulation is 0.901 g/cm³, and the silane component amount inthe resin component of the same layer is 0.056% by mass.

Encapsulant Composition for Second Layer (Base Layer): The following“additive resin 1 (weatherproofing agent master batch)” and “additiveresin 2 (silane-modified polyethylene)” were mixed in the proportions of5 parts by mass and 1 part by mass, respectively, relative to 94 partsby mass of the following “base resin 1”. The density of the second layer(base layer) of the encapsulant sheet of Example 3-1 consisting of theabove formulation is 0.902 g/cm³, and the silane component amount in theresin component of the same layer is 0.004% by mass.

Encapsulant Composition of Third Layer (Non-Adhesive Layer): Thefollowing “additive resin 1 (weatherproofing agent master batch)” and“additive resin 2 (silane-modified polyethylene)” were mixed in theproportions of 5 parts by mass and 0 parts by mass, respectively,relative to 95 parts by mass of the following “base resin 1”. Thedensity of the third layer (non-adhesive layer) of the encapsulant sheetof Example 3-1 consisting of the above formulation is 0.902 g/cm³, andthe silane component amount in the resin component of the same layer is0% by mass. The encapsulant sheet of Example 3-1 was made by coextrudingthe above-mentioned first layer-second layer-third layer in thicknessratio of each layer of 1:8:1, and total thickness of all layers of 150μm.

Encapsulant Sheet of Example 3-2

The encapsulant sheet of Example 3-2 was made by coextruding theabove-mentioned first layer-second layer-third layer using the samematerials as the compositions for each layer used in Example 3-1, inthickness ratio of each layer of 1:6:1, and total thickness of alllayers of 600 μm.

Encapsulant Sheet of Example 3-3

The encapsulant sheet of Example 3-3 was made by coextruding theabove-mentioned first layer-second layer-third layer using the samematerials as the compositions for each layer used in Example 3-1, inthickness ratio of each layer of 1:5:1, and total thickness of alllayers of 70 μm.

Encapsulant Sheet of Comparative Example 3-1

Encapsulant Composition for First Layer (Adhesive Layer): The following“additive resin 1 (weatherproofing agent master batch)” and “additiveresin 2 (silane-modified polyethylene)” were mixed in the proportions of5 parts by mass and 15 parts by mass, respectively, relative to 80 partsby mass of the following “base resin 1”. The density of the first layer(adhesive layer) of the encapsulant sheet of Comparative Example 3-1consisting of the above formulation is 0.901 g/cm³, and the silanecomponent amount in the resin component of the same layer is 0.056% bymass.

Encapsulant Composition for Second Layer (Base Layer): The following“additive resin 1 (weatherproofing agent master batch)” and “additiveresin 2 (silane-modified polyethylene)” were mixed in the proportions of5 parts by mass and 1 parts by mass, respectively, relative to 94 partsby mass of the following “base resin 1”. The density of the second layer(base layer) of the encapsulant sheet of Comparative Example 3-1consisting of the above formulation is 0.902 g/cm³, and the silanecomponent amount in the resin component of the same layer is 0.004% bymass.

Encapsulant Composition for Third Layer: The same composition as thefirst layer was used. The encapsulant sheet of Comparative Example 3-1was made by coextruding the above-mentioned first layer-secondlayer-third layer, in thickness ratio of each layer of 1:8:1, and totalthickness of all layers of 150 μm.

Encapsulant Sheet of Comparative Example 3-2

Encapsulant Composition for First Layer (Non-adhesive Layer): Thefollowing “additive resin 1 (weatherproofing agent master batch)” and“additive resin 2 (silane-modified polyethylene)” were mixed in theproportions of 5 parts by mass and 0 parts by mass, respectively,relative to 95 parts by mass of the following “base resin 1”. Thedensity of the first layer (non-adhesive layer) of the encapsulant sheetof Comparative Example 3-2 consisting of the above formulation is 0.902g/cm³, and the silane component amount in the resin component of thesame layer is 0% by mass.

Encapsulant Composition for Second Layer (Base Layer): The following“additive resin 1 (weatherproofing agent master batch)” and “additiveresin 2 (silane-modified polyethylene)” were mixed in the proportions of5 parts by mass and 1 parts by mass, respectively, relative to 94 partsby mass of the following “base resin 1”. The density of the second layer(base layer) of the encapsulant sheet of Comparative Example 3-2consisting of the above formulation is 0.902 g/cm³, and the silanecomponent amount in the resin component of the same layer is 0.004% bymass.

Encapsulant Composition for Third Layer: The same composition as thefirst layer was used. The encapsulant sheet of Comparative Example 3-2was made by coextruding the above-mentioned first layer-secondlayer-third layer, in thickness ratio of each layer of 1:8:1, and totalthickness of all layers of 150 μm.

The following resin material was used in the production of each of theabove-mentioned encapsulant sheet in the third examples.

-   -   Base Resin 1: Metallocene linear low-density polyethylene        (M-LLDPE) with density of 0.901 g/cm³, melting point of 93° C.,        and MFR at 190° C. of 2.0 g/10 min.    -   Additive Resin 1 (weatherproofing agent master batch): Relative        to 100 parts by mass of low-density polyethylene with 0.919        g/cm³ density and MFR at 190° C. of 3.5 g/10 min, KEMIS    -   TAB62(HALS): 0.6 parts by mass.    -   KEMISORB12 (UV absorber): 3.5 parts by mass    -   KEMISORB79 (UV absorber): 0.6 parts by mass    -   Additive Resin 2 (silane-modified polyethylene): Silane-modified        polyethylene obtained by mixing 5 parts by mass of vinyl        trimethoxysilane and 0.15 parts by mass of dicumylperoxide as a        radical generator (reaction catalyst) relative to 100 parts by        mass of metallocene linear low-density polyethylene having a        density of 0.898 g/cm³ and MFR of 3.5 g/10 min, then melting at        200° C. and kneading. The density of this additive resin 2 is        0.901 g/cm³, and MFR is 1.0 g/10 min.        <Evaluation of Encapsulant Sheet>

Evaluation Example 1: Adhesive Strength (Adhesive Surface and PeelingSurface

For each encapsulant sheet of the Examples and Comparative Examples, thefollowing adhesion test was performed in order to measure the adhesivestrength of each surface. The results were as noted in Table 3. AdhesionTest: Lamination processing was performed in a vacuum heated laminatorat 140° C. for 10 minutes by adhering the first layer of eachencapsulant sheet sample cut to the size of 75×50 mm on blue-sheet glass(75 mm×50 mm×3 mm), and in a state penetrating to immediately above theblue-sheet glass plate surface with 15 mm width in the encapsulant sheetsample adhered on the glass epoxy plate, making a cut serving as thestart for the peeling start location, and then performing a verticalpeeling (50 mm/min) test with a peel testing machine (Tensilon universaltesting machine RTF-1150-H) to measure the adhesive strength of theadhesive surface. In addition, for the Examples, the same test wasperformed by adhering the third layer of each of the above-mentionedencapsulant sheet material onto blue-sheet glass (75 mm×50 mm×3 mm) tomeasure the adhesive strength of the peeling surface. The evaluationresults are noted in Table 3 as “Adhesive strength”.

Evaluation Example 2: Peeling Property after Thermal Lamination

For each encapsulant sheet of the Examples and Comparative Examples, anoperation of tearing away the encapsulant sheet by manual operation fromthe glass plate was performed at the interface of the encapsulantsheet/blue-sheet glass, after adhering the third layer onto theblue-sheet glass (75 mm×50 mm×3 mm) at the same conditions as theabove-mentioned adhesion test, the state of the interface after tearingaway was observed visually, and the peeling property after thermallamination was evaluated based on the following evaluation criteria. Theevaluation results are noted in Table 3 as “peeling property”.

Evaluation Criteria

-   -   A: Peeling off of the encapsulant sheet by manual operation        could be easily performed. In addition, cohesive peeling of        encapsulant sheet at edge part of peeling area of encapsulant        sheet was not observed.    -   C: Peeling off of encapsulant sheet by manual operation was        somewhat difficult, and cohesive peeling of encapsulant sheet at        edge part of peeling area of encapsulant sheet was not observed.        (Reference Test)

It should be noted that, as the reference test, the encapsulant sheet ofComparative Example 3-1 was laminated on the above-mentioned blue-sheetglass via a release film (38 μm thickness) consisting of polyethyleneterephthalate, and testing and evaluation of the same conditions wereperformed; however, if the evaluation according to the followingevaluation criteria for “releasability after thermal lamination” of theencapsulant sheet of the Comparative Examples in the case of thisreference test being “A”, i.e. even if the encapsulant sheet ofComparative Example 3-1, it was confirmed that it could be releasedwithout problems so long as using the release film.

Evaluation Example 3: Molding Property

For each encapsulant sheet of the Examples and Comparative Examples, themolding property to an uneven surface was evaluated by the followingtest method. Module Preparation for Molding Property Test: A pseudo LEDmodule made by molding a thermosetting-type epoxy resin so as to havethe same external form as an LED element of the micro size of 25 μmwidth×15 μm depth×2.5 μm height and arranging at a pitch of 2 mm on thesurface of a glass epoxy substrate of 200×300-mm size is prepared, thefirst layer any encapsulant sheet of the respective Examples andComparative Examples is laminated to opposed the pseudo LED elementarrangement surface of this module, and a 50-μm ethylenetetrafluoroethylene (ETFE) film which has been single-side coronatreated was further laminated on this encapsulant sheet as a surfaceprotective film, vacuum lamination processing was performed atconditions of 150° C., 5 minutes vacuum drawing, 10 minutes pressholding at 70 KPa upper chamber pressure, using a vacuum laminator forsolar cell module manufacturing, thereby creating a module for moldingproperty testing. Molding

Property Test:

Each of the above-mentioned modules for testing was visually observed toevaluate the molding property based on the following evaluationcriteria. The evaluation results are noted in Table 3 as “Moldingproperty”.

Evaluation Criteria

-   -   A: Perfectly followed unevenness of LED element arrangement        surface opposed by encapsulant sheet. Formation of voids was not        observed.    -   B: No more than three bubbles of no more than 2 mm² observed.    -   C: Does not perfectly follow unevenness of LED element        arrangement surface opposed by part of encapsulant sheet, and        partially laminated defective portion (void) formed in vicinity        of pseudo LED element.

Evaluation Example 4: Heat Resistance

For each encapsulant sheet of the Examples and Comparative Examples, theheat resistance after vacuum lamination carried out in theabove-mentioned molding test was evaluated by the following test method.

-   -   Heat Resistance Test: The encapsulant sheet prepared in the        Examples and Comparative Examples was sandwiched between a        30×30-cm glass of 3 mm thickness, and a 50×75-cm glass of 3 mm        thickness, vacuum lamination processing was performed at        conditions of 150° C., 5 minutes vacuum drawing, 10 minutes        press holding at 70 KPa upper chamber pressure, using a vacuum        laminator for solar cell module manufacturing, and subsequently,        was cooled until room temperature to prepare a heat resistance        test piece. Subsequently, the cooled test piece was placed        vertically in a convection circulation oven at 85° C., and        measurement was performed for the shift amount between before        charging into the oven and after taking out the 50×75-mm glass        of 3-mm thickness after 1000 hours. The heat resistance was        evaluated based on the following evaluation criteria for the        measurement results. The evaluation results are noted in Table 3        as “Heat resistance”.        Evaluation Criteria    -   A: Shift amount less than 1 mm    -   B: Shift amount at least 1 mm and less than 10 mm    -   C: Shift amount at least 10 mm

TABLE 3 Adhesive strength Silane component (N/15 mm) (mass %) MoldingHeat First layer Third layer First layer Second layer Third layerReleasability property resistance Example1 11.5 0.2 0.056 0.004 0 A A AExample2 4.3 0.3 0.056 0.004 0 A A A Example3 7.5 0.1 0.056 0.004 0 A AA Comparative 12.5 12.8 0.056 0.004 0.056 C A A Example1 Comparative 0.30.3 0 0.004 0 A C A Example2

According to Table 3, the encapsulant sheet for self-luminous displaysof the Third Example was found to be an encapsulant sheet capable ofproducing an LED module for self-luminous displays with higherproductivity while maintaining at least equal quality as conventional,even without using a mold release film.

EXPLANATION OF REFERENCE NUMERALS

-   -   1 encapsulant sheet    -   111 base layer    -   121 non-adhesive layer    -   122 adhesive layer    -   123 peeling surface    -   124 adhesive surface    -   10 LED element    -   11 LED light emitting chip    -   12 resin cover    -   13 light diffusing lens    -   20 wiring substrate    -   21 support substrate    -   22 wiring part    -   23 solder layer    -   24 adhesive layer    -   25 insulative protective film    -   26 reflective layer    -   30 LED module    -   40 laminator    -   41 heating plate    -   42 heating plate (auxiliary heating plate)    -   43 laminate body holding plate    -   2 display panel    -   5 diffuser    -   100, 100A, 100B micro LED display device (self-luminous display)    -   200 direct LED backlight    -   300 liquid crystal display (direct backlight type)

The invention claimed is:
 1. An encapsulant sheet for self-luminousdisplay or for direct backlights, wherein the encapsulant sheet is asingle-layer or a multi-layer resin sheet that includes an adhesivelayer exposed at a topmost surface, wherein Vicat softening point isgreater than 60° C. and no higher than 100° C., wherein melt viscosityof the encapsulant sheet at a shear rate of 2.43×10 sec⁻¹ measured at atemperature of 120° C. is at least 5.0×10⁴ poise and no more than1.0×10⁵ poise, wherein the adhesive layer contains a polyolefin and asilane component, and wherein content of the silane component relativeto resin component of the adhesive layer is at least 0.03% by mass andless than 10% by mass.
 2. The encapsulant sheet according to claim 1,wherein the silane component includes a graft silane component whichgraft-polymerizes to the polyolefin of the adhesive layer, wherein theadhesive layer contains at least 70% by mass and no more than 100% bymass of the graft silane.
 3. The encapsulant sheet according to claim 1,wherein the encapsulant sheet is a multi-layer resin sheet in which theadhesive layer is laminated on a base layer with polyethylene as a baseresin.
 4. The encapsulant sheet according to claim 1, wherein meltviscosity of the encapsulant sheet measured at a shear rate of 2.43×10sec⁻¹ and measured at a temperature of 120° C. is at least 5.0×10⁴ poiseand no more than 1.0×10⁵ poise.
 5. The encapsulant sheet according toclaim 1, wherein the encapsulant sheet has a thickness of at least 25 μmand no more than 100 μm.
 6. The encapsulant sheet according to claim 1,wherein the encapsulant sheet is a resin sheet which is black, white oranother color.
 7. The encapsulant sheet according to claim 1, whereinone surface is an adhesive surface, and the other surface is a peelingsurface, wherein adhesive strength of the adhesive surface measured byan adhesion test is at least 5.0 N/15 mm and no more than 50.0 N/15 mm,wherein the adhesive strength of the peeling surface is at least 0.1N/15 mm and no more than 3.0 N/15 mm, and wherein the adhesion testmeasures adhesive strength of each surface by adhering a surface on aside serving as a measurement target of an encapsulant sheet sample cutto a width of 15 mm onto a blue-sheet glass plate (75 mm×50 mm×3 mm) andperforming laminate treatment in a vacuum heated laminator at 140° C.for 10 minutes, and performing a vertical peeling (50 mm/min) test witha peel tester on the encapsulant sheet sample adhered on the blue-sheetglass plate.
 8. The encapsulant sheet according to claim 7, wherein theencapsulant sheet is a multi-layer resin sheet having the adhesive layerexposed at a surface on a side of the adhesive surface, and anon-adhesive layer exposed at a surface on a side of the peelingsurface, wherein the adhesive layer contains a silane component in aproportion of at least 0.02% by mass and no more than 0.19% by massrelative to a resin component of the adhesive layer, and wherein thenon-adhesive layer does not contain the silane component, or in a caseof containing the silane component, a content of the silane componentrelative to the resin component is less than 0.02% by mass.
 9. Theencapsulant sheet according to claim 8, wherein the encapsulant sheet isa multi-layer resin sheet in which the adhesive layer is laminated onone surface of the base layer with polyethylene as base resin, and thenon-adhesive layer is laminated on the other surface of the base layer.10. A self-luminous display comprising: the encapsulant sheet accordingto claim 1; a display panel; and a light emitting module in which aplurality of light emitting elements is mounted to a wiring substrate,wherein the encapsulant sheet is laminated to the light emitting moduleto cover the light emitting elements and the wiring substrate, andwherein the display panel is laminated to the encapsulant sheet.
 11. Theself-luminous display according to claim 10, wherein the light emittingelements are LED elements, wherein at least one of the LED elementsincludes an LED light emitting chip and a resin cover which covers theLED light emitting chip, wherein a width and a depth of the at least oneLED element are both no more than 300 μm, and a height is no more than200 μm, and wherein an arrangement interval of each of the LED elementsis at least 0.03 mm and no more than 100 mm.
 12. The self-luminousdisplay according to claim 11, wherein the width and the depth of the atleast one the LED element are both no more than 50 μm, and the height isno more than 10 μm, and wherein the arrangement interval of each of theLED elements is at least 0.05 mm and no more than 5 mm.
 13. Theself-luminous display according to claim 11, further comprising a lightemitting surface made by a plurality of light emitting modules includingthe light emitting module being joined on the same plane, wherein theencapsulant sheet is laminated on the light emitting surface.
 14. Adirect backlight comprising: the encapsulant sheet according to claim 1;and a light emitting module in which a plurality of light emittingelements is mounted to a wiring substrate, wherein the encapsulant sheetis laminated to the light emitting module to cover the light emittingelement and the wiring substrate.
 15. The direct backlight according toclaim 14, wherein the light emitting elements are LED elements, whereinat least one of the LED elements includes an LED light emitting chip anda resin cover which covers the LED light emitting chip, wherein a widthand a depth of the at least one LED element are both no more than 300μm, and a height is no more than 200 μm, and wherein an arrangementinterval of each of the LED elements is at least 0.03 mm and no morethan 100 mm.
 16. The direct backlight according to claim 15, wherein thewidth and the depth of the at least one LED element are both no morethan 50 μm, and the height is no more than 10 μm, and wherein thearrangement interval of each of the LED elements is at least 0.05 mm andno more than 5 mm.
 17. The direct backlight according to claim 15,further comprising a light emitting surface made by a plurality of lightemitting modules including the light emitting module being joined on thesame plane, wherein the encapsulant sheet is laminated on the lightemitting surface.
 18. An LED display device comprising: the directbacklight according to claim 15; a diffusion plate; and a display panel,wherein one surface of the encapsulant sheet configuring the directbacklight is an adhesive surface and another surface thereof is apeeling surface, and wherein the diffusion plate is laminated to thepeeling surface of the encapsulant sheet.